ws

README

ws

RFC6455 WebSocket implementation in Go.

Features

• Zero-copy upgrade
• No intermediate allocations during I/O
• Low-level API which allows to build your own logic of packet handling and buffers reuse
• High-level wrappers and helpers around API in wsutil package, which allow to start fast without digging the protocol internals

Documentation

GoDoc.

Why

Existing WebSocket implementations do not allow users to reuse I/O buffers between connections in clear way. This library aims to export efficient low-level interface for working with the protocol without forcing only one way it could be used.

By the way, if you want get the higher-level tools, you can use wsutil package.

Status

Library is tagged as v1* so its API must not be broken during some improvements or refactoring.

This implementation of RFC6455 passes Autobahn Test Suite and currently has about 78% coverage.

Examples

Example applications using ws are developed in separate repository ws-examples.

Usage

The higher-level example of WebSocket echo server:

package main

import (
	"net/http"

	"github.com/gobwas/ws"
	"github.com/gobwas/ws/wsutil"
)

func main() {
	http.ListenAndServe(":8080", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		conn, _, _, err := ws.UpgradeHTTP(r, w)
		if err != nil {
			// handle error
		}
		go func() {
			defer conn.Close()

			for {
				msg, op, err := wsutil.ReadClientData(conn)
				if err != nil {
					// handle error
				}
				err = wsutil.WriteServerMessage(conn, op, msg)
				if err != nil {
					// handle error
				}
			}
		}()
	}))
}

Lower-level, but still high-level example:

import (
	"net/http"
	"io"

	"github.com/gobwas/ws"
	"github.com/gobwas/ws/wsutil"
)

func main() {
	http.ListenAndServe(":8080", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		conn, _, _, err := ws.UpgradeHTTP(r, w)
		if err != nil {
			// handle error
		}
		go func() {
			defer conn.Close()

			var (
				state  = ws.StateServerSide
				reader = wsutil.NewReader(conn, state)
				writer = wsutil.NewWriter(conn, state, ws.OpText)
			)
			for {
				header, err := reader.NextFrame()
				if err != nil {
					// handle error
				}

				// Reset writer to write frame with right operation code.
				writer.Reset(conn, state, header.OpCode)

				if _, err = io.Copy(writer, reader); err != nil {
					// handle error
				}
				if err = writer.Flush(); err != nil {
					// handle error
				}
			}
		}()
	}))
}

We can apply the same pattern to read and write structured responses through a JSON encoder and decoder.:

	...
	var (
		r = wsutil.NewReader(conn, ws.StateServerSide)
		w = wsutil.NewWriter(conn, ws.StateServerSide, ws.OpText)
		decoder = json.NewDecoder(r)
		encoder = json.NewEncoder(w)
	)
	for {
		hdr, err = r.NextFrame()
		if err != nil {
			return err
		}
		if hdr.OpCode == ws.OpClose {
			return io.EOF
		}
		var req Request
		if err := decoder.Decode(&req); err != nil {
			return err
		}
		var resp Response
		if err := encoder.Encode(&resp); err != nil {
			return err
		}
		if err = w.Flush(); err != nil {
			return err
		}
	}
	...

The lower-level example without wsutil:

package main

import (
	"net"
	"io"

	"github.com/gobwas/ws"
)

func main() {
	ln, err := net.Listen("tcp", "localhost:8080")
	if err != nil {
		log.Fatal(err)
	}

	for {
		conn, err := ln.Accept()
		if err != nil {
			// handle error
		}
		_, err = ws.Upgrade(conn)
		if err != nil {
			// handle error
		}

		go func() {
			defer conn.Close()

			for {
				header, err := ws.ReadHeader(conn)
				if err != nil {
					// handle error
				}

				payload := make([]byte, header.Length)
				_, err = io.ReadFull(conn, payload)
				if err != nil {
					// handle error
				}
				if header.Masked {
					ws.Cipher(payload, header.Mask, 0)
				}

				// Reset the Masked flag, server frames must not be masked as
				// RFC6455 says.
				header.Masked = false

				if err := ws.WriteHeader(conn, header); err != nil {
					// handle error
				}
				if _, err := conn.Write(payload); err != nil {
					// handle error
				}

				if header.OpCode == ws.OpClose {
					return
				}
			}
		}()
	}
}

Zero-copy upgrade

Zero-copy upgrade helps to avoid unnecessary allocations and copying while handling HTTP Upgrade request.

Processing of all non-websocket headers is made in place with use of registered user callbacks whose arguments are only valid until callback returns.

The simple example looks like this:

package main

import (
	"net"
	"log"

	"github.com/gobwas/ws"
)

func main() {
	ln, err := net.Listen("tcp", "localhost:8080")
	if err != nil {
		log.Fatal(err)
	}
	u := ws.Upgrader{
		OnHeader: func(key, value []byte) (err error) {
			log.Printf("non-websocket header: %q=%q", key, value)
			return
		},
	}
	for {
		conn, err := ln.Accept()
		if err != nil {
			// handle error
		}

		_, err = u.Upgrade(conn)
		if err != nil {
			// handle error
		}
	}
}

Usage of ws.Upgrader here brings ability to control incoming connections on tcp level and simply not to accept them by some logic.

Zero-copy upgrade is for high-load services which have to control many resources such as connections buffers.

The real life example could be like this:

package main

import (
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"runtime"

	"github.com/gobwas/httphead"
	"github.com/gobwas/ws"
)

func main() {
	ln, err := net.Listen("tcp", "localhost:8080")
	if err != nil {
		// handle error
	}

	// Prepare handshake header writer from http.Header mapping.
	header := ws.HandshakeHeaderHTTP(http.Header{
		"X-Go-Version": []string{runtime.Version()},
	})

	u := ws.Upgrader{
		OnHost: func(host []byte) error {
			if string(host) == "github.com" {
				return nil
			}
			return ws.RejectConnectionError(
				ws.RejectionStatus(403),
				ws.RejectionHeader(ws.HandshakeHeaderString(
					"X-Want-Host: github.com\r\n",
				)),
			)
		},
		OnHeader: func(key, value []byte) error {
			if string(key) != "Cookie" {
				return nil
			}
			ok := httphead.ScanCookie(value, func(key, value []byte) bool {
				// Check session here or do some other stuff with cookies.
				// Maybe copy some values for future use.
				return true
			})
			if ok {
				return nil
			}
			return ws.RejectConnectionError(
				ws.RejectionReason("bad cookie"),
				ws.RejectionStatus(400),
			)
		},
		OnBeforeUpgrade: func() (ws.HandshakeHeader, error) {
			return header, nil
		},
	}
	for {
		conn, err := ln.Accept()
		if err != nil {
			log.Fatal(err)
		}
		_, err = u.Upgrade(conn)
		if err != nil {
			log.Printf("upgrade error: %s", err)
		}
	}
}

Compression

There is a ws/wsflate package to support Permessage-Deflate Compression Extension.

It provides minimalistic I/O wrappers to be used in conjunction with any deflate implementation (for example, the standard library's compress/flate).

It is also compatible with wsutil's reader and writer by providing wsflate.MessageState type, which implements wsutil.SendExtension and wsutil.RecvExtension interfaces.

package main

import (
	"bytes"
	"log"
	"net"

	"github.com/gobwas/ws"
	"github.com/gobwas/ws/wsflate"
)

func main() {
	ln, err := net.Listen("tcp", "localhost:8080")
	if err != nil {
		// handle error
	}
	e := wsflate.Extension{
		// We are using default parameters here since we use
		// wsflate.{Compress,Decompress}Frame helpers below in the code.
		// This assumes that we use standard compress/flate package as flate
		// implementation.
		Parameters: wsflate.DefaultParameters,
	}
	u := ws.Upgrader{
		Negotiate: e.Negotiate,
	}
	for {
		conn, err := ln.Accept()
		if err != nil {
			log.Fatal(err)
		}

		// Reset extension after previous upgrades.
		e.Reset()

		_, err = u.Upgrade(conn)
		if err != nil {
			log.Printf("upgrade error: %s", err)
			continue
		}
		if _, ok := e.Accepted(); !ok {
			log.Printf("didn't negotiate compression for %s", conn.RemoteAddr())
			conn.Close()
			continue
		}

		go func() {
			defer conn.Close()
			for {
				frame, err := ws.ReadFrame(conn)
				if err != nil {
					// Handle error.
					return
				}

				frame = ws.UnmaskFrameInPlace(frame)

				if wsflate.IsCompressed(frame.Header) {
					// Note that even after successful negotiation of
					// compression extension, both sides are able to send
					// non-compressed messages.
					frame, err = wsflate.DecompressFrame(frame)
					if err != nil {
						// Handle error.
						return
					}
				}

				// Do something with frame...

				ack := ws.NewTextFrame([]byte("this is an acknowledgement"))

				// Compress response unconditionally.
				ack, err = wsflate.CompressFrame(ack)
				if err != nil {
					// Handle error.
					return
				}
				if err = ws.WriteFrame(conn, ack); err != nil {
					// Handle error.
					return
				}
			}
		}()
	}
}

You can use compression with wsutil package this way:

	// Upgrade somehow and negotiate compression to get the conn...

	// Initialize flate reader. We are using nil as a source io.Reader because
	// we will Reset() it in the message i/o loop below.
	fr := wsflate.NewReader(nil, func(r io.Reader) wsflate.Decompressor {
		return flate.NewReader(r)
	})
	// Initialize flate writer. We are using nil as a destination io.Writer
	// because we will Reset() it in the message i/o loop below.
	fw := wsflate.NewWriter(nil, func(w io.Writer) wsflate.Compressor {
		f, _ := flate.NewWriter(w, 9)
		return f
	})

	// Declare compression message state variable.
	//
	// It has two goals:
	// - Allow users to check whether received message is compressed or not.
	// - Help wsutil.Reader and wsutil.Writer to set/unset appropriate
	//   WebSocket header bits while writing next frame to the wire (it
	//   implements wsutil.RecvExtension and wsutil.SendExtension).
	var msg wsflate.MessageState

	// Initialize WebSocket reader as previously. 
	// Please note the use of Reader.Extensions field as well as
	// of ws.StateExtended flag.
	rd := &wsutil.Reader{
		Source:     conn,
		State:      ws.StateServerSide | ws.StateExtended,
		Extensions: []wsutil.RecvExtension{
			&msg, 
		},
	}

	// Initialize WebSocket writer with ws.StateExtended flag as well.
	wr := wsutil.NewWriter(conn, ws.StateServerSide|ws.StateExtended, 0)
	// Use the message state as wsutil.SendExtension.
	wr.SetExtensions(&msg)

	for {
		h, err := rd.NextFrame()
		if err != nil {
			// handle error.
		}
		if h.OpCode.IsControl() {
			// handle control frame.
		}
		if !msg.IsCompressed() {
			// handle uncompressed frame (skipped for the sake of example
			// simplicity).
		}

		// Reset the writer to echo same op code.
		wr.Reset(h.OpCode)

		// Reset both flate reader and writer to start the new round of i/o.
		fr.Reset(rd)
		fw.Reset(wr)

		// Copy whole message from reader to writer decompressing it and
		// compressing again.
		if _, err := io.Copy(fw, fr); err != nil {
			// handle error.
		}
		// Flush any remaining buffers from flate writer to WebSocket writer.
		if err := fw.Close(); err != nil {
			// handle error.
		}
		// Flush the whole WebSocket message to the wire.
		if err := wr.Flush(); err != nil {
			// handle error.
		}
	}

Documentation

Overview

Package ws implements a client and server for the WebSocket protocol as specified in RFC 6455.

The main purpose of this package is to provide simple low-level API for efficient work with protocol.

Overview.

Upgrade to WebSocket (or WebSocket handshake) can be done in two ways.

The first way is to use `net/http` server:

http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
	conn, _, _, err := ws.UpgradeHTTP(r, w)
})

The second and much more efficient way is so-called "zero-copy upgrade". It avoids redundant allocations and copying of not used headers or other request data. User decides by himself which data should be copied.

ln, err := net.Listen("tcp", ":8080")
if err != nil {
	// handle error
}

conn, err := ln.Accept()
if err != nil {
	// handle error
}

handshake, err := ws.Upgrade(conn)
if err != nil {
	// handle error
}

For customization details see `ws.Upgrader` documentation.

After WebSocket handshake you can work with connection in multiple ways. That is, `ws` does not force the only one way of how to work with WebSocket:

header, err := ws.ReadHeader(conn)
if err != nil {
	// handle err
}

buf := make([]byte, header.Length)
_, err := io.ReadFull(conn, buf)
if err != nil {
	// handle err
}

resp := ws.NewBinaryFrame([]byte("hello, world!"))
if err := ws.WriteFrame(conn, frame); err != nil {
    // handle err
}

As you can see, it stream friendly:

const N = 42

ws.WriteHeader(ws.Header{
	Fin:    true,
	Length: N,
	OpCode: ws.OpBinary,
})

io.CopyN(conn, rand.Reader, N)

Or:

header, err := ws.ReadHeader(conn)
if err != nil {
	// handle err
}

io.CopyN(ioutil.Discard, conn, header.Length)

For more info see the documentation.

Index

• Constants
• Variables
• func CheckCloseFrameData(code StatusCode, reason string) error
• func CheckHeader(h Header, s State) error
• func Cipher(payload []byte, mask [4]byte, offset int)
• func CompileFrame(f Frame) (bts []byte, err error)
• func HeaderSize(h Header) (n int)
• func MustCompileFrame(f Frame) []byte
• func MustWriteFrame(w io.Writer, f Frame)
• func NewCloseFrameBody(code StatusCode, reason string) []byte
• func NewMask() (ret [4]byte)
• func PutCloseFrameBody(p []byte, code StatusCode, reason string)
• func PutReader(br *bufio.Reader)
• func RejectConnectionError(options ...RejectOption) error
• func Rsv(r1, r2, r3 bool) (rsv byte)
• func RsvBits(rsv byte) (r1, r2, r3 bool)
• func SelectEqual(v string) func(string) bool
• func SelectFromSlice(accept []string) func(string) bool
• func WriteFrame(w io.Writer, f Frame) error
• func WriteHeader(w io.Writer, h Header) error
• type ConnectionRejectedError
  • func (r *ConnectionRejectedError) Error() string
  • func (r *ConnectionRejectedError) StatusCode() int
• type Dialer
  • func (d Dialer) Dial(ctx context.Context, urlstr string) (conn net.Conn, br *bufio.Reader, hs Handshake, err error)
  • func (d Dialer) Upgrade(conn io.ReadWriter, u *url.URL) (br *bufio.Reader, hs Handshake, err error)
• type Frame
  • func MaskFrame(f Frame) Frame
  • func MaskFrameInPlace(f Frame) Frame
  • func MaskFrameInPlaceWith(f Frame, m [4]byte) Frame
  • func MaskFrameWith(f Frame, mask [4]byte) Frame
  • func MustReadFrame(r io.Reader) Frame
  • func NewBinaryFrame(p []byte) Frame
  • func NewCloseFrame(p []byte) Frame
  • func NewFrame(op OpCode, fin bool, p []byte) Frame
  • func NewPingFrame(p []byte) Frame
  • func NewPongFrame(p []byte) Frame
  • func NewTextFrame(p []byte) Frame
  • func ReadFrame(r io.Reader) (f Frame, err error)
  • func UnmaskFrame(f Frame) Frame
  • func UnmaskFrameInPlace(f Frame) Frame
• type HTTPUpgrader
  • func (u HTTPUpgrader) Upgrade(r *http.Request, w http.ResponseWriter) (conn net.Conn, rw *bufio.ReadWriter, hs Handshake, err error)
• type Handshake
  • func Dial(ctx context.Context, urlstr string) (net.Conn, *bufio.Reader, Handshake, error)
  • func Upgrade(conn io.ReadWriter) (Handshake, error)
  • func UpgradeHTTP(r *http.Request, w http.ResponseWriter) (net.Conn, *bufio.ReadWriter, Handshake, error)
• type HandshakeHeader
• type HandshakeHeaderBytes
  • func (b HandshakeHeaderBytes) WriteTo(w io.Writer) (int64, error)
• type HandshakeHeaderFunc
  • func (f HandshakeHeaderFunc) WriteTo(w io.Writer) (int64, error)
• type HandshakeHeaderHTTP
  • func (h HandshakeHeaderHTTP) WriteTo(w io.Writer) (int64, error)
• type HandshakeHeaderString
  • func (s HandshakeHeaderString) WriteTo(w io.Writer) (int64, error)
• type Header
  • func ReadHeader(r io.Reader) (h Header, err error)
  • func (h Header) Rsv1() bool
  • func (h Header) Rsv2() bool
  • func (h Header) Rsv3() bool
• type OpCode
  • func (c OpCode) IsControl() bool
  • func (c OpCode) IsData() bool
  • func (c OpCode) IsReserved() bool
• type ProtocolError
  • func (p ProtocolError) Error() string
• type RejectOption
  • func RejectionHeader(h HandshakeHeader) RejectOption
  • func RejectionReason(reason string) RejectOption
  • func RejectionStatus(code int) RejectOption
• type State
  • func (s State) Clear(v State) State
  • func (s State) ClientSide() bool
  • func (s State) Extended() bool
  • func (s State) Fragmented() bool
  • func (s State) Is(v State) bool
  • func (s State) ServerSide() bool
  • func (s State) Set(v State) State
• type StatusCode
  • func ParseCloseFrameData(payload []byte) (code StatusCode, reason string)
  • func ParseCloseFrameDataUnsafe(payload []byte) (code StatusCode, reason string)
  • func (s StatusCode) Empty() bool
  • func (s StatusCode) In(r StatusCodeRange) bool
  • func (s StatusCode) IsApplicationSpec() bool
  • func (s StatusCode) IsNotUsed() bool
  • func (s StatusCode) IsPrivateSpec() bool
  • func (s StatusCode) IsProtocolDefined() bool
  • func (s StatusCode) IsProtocolReserved() bool
  • func (s StatusCode) IsProtocolSpec() bool
• type StatusCodeRange
• type StatusError
  • func (s StatusError) Error() string
• type Upgrader
  • func (u Upgrader) Upgrade(conn io.ReadWriter) (hs Handshake, err error)

Constants

const (
	DefaultClientReadBufferSize  = 4096
	DefaultClientWriteBufferSize = 4096
)

Constants used by Dialer.

const (
	DefaultServerReadBufferSize  = 4096
	DefaultServerWriteBufferSize = 512
)

Constants used by ConnUpgrader.

const (
	MaxHeaderSize = 14
	MinHeaderSize = 2
)

Header size length bounds in bytes.

const (
	// All control frames MUST have a payload length of 125 bytes or less and MUST NOT be fragmented.
	MaxControlFramePayloadSize = 125
)

Constants defined by specification.

Variables

var (
	ErrProtocolOpCodeReserved             = ProtocolError("use of reserved op code")
	ErrProtocolControlPayloadOverflow     = ProtocolError("control frame payload limit exceeded")
	ErrProtocolControlNotFinal            = ProtocolError("control frame is not final")
	ErrProtocolNonZeroRsv                 = ProtocolError("non-zero rsv bits with no extension negotiated")
	ErrProtocolMaskRequired               = ProtocolError("frames from client to server must be masked")
	ErrProtocolMaskUnexpected             = ProtocolError("frames from server to client must be not masked")
	ErrProtocolContinuationExpected       = ProtocolError("unexpected non-continuation data frame")
	ErrProtocolContinuationUnexpected     = ProtocolError("unexpected continuation data frame")
	ErrProtocolStatusCodeNotInUse         = ProtocolError("status code is not in use")
	ErrProtocolStatusCodeApplicationLevel = ProtocolError("status code is only application level")
	ErrProtocolStatusCodeNoMeaning        = ProtocolError("status code has no meaning yet")
	ErrProtocolStatusCodeUnknown          = ProtocolError("status code is not defined in spec")
	ErrProtocolInvalidUTF8                = ProtocolError("invalid utf8 sequence in close reason")
)

Errors used by the protocol checkers.

var (
	ErrHandshakeBadStatus      = fmt.Errorf("unexpected http status")
	ErrHandshakeBadSubProtocol = fmt.Errorf("unexpected protocol in %q header", headerSecProtocol)
	ErrHandshakeBadExtensions  = fmt.Errorf("unexpected extensions in %q header", headerSecProtocol)
)

Errors used by the websocket client.

var (
	StatusRangeNotInUse    = StatusCodeRange{0, 999}
	StatusRangeProtocol    = StatusCodeRange{1000, 2999}
	StatusRangeApplication = StatusCodeRange{3000, 3999}
	StatusRangePrivate     = StatusCodeRange{4000, 4999}
)

Status code ranges defined by specification. See https://tools.ietf.org/html/rfc6455#section-7.4.2

var (
	CompiledPing  = MustCompileFrame(NewPingFrame(nil))
	CompiledPong  = MustCompileFrame(NewPongFrame(nil))
	CompiledClose = MustCompileFrame(NewCloseFrame(nil))

	CompiledCloseNormalClosure           = MustCompileFrame(closeFrameNormalClosure)
	CompiledCloseGoingAway               = MustCompileFrame(closeFrameGoingAway)
	CompiledCloseProtocolError           = MustCompileFrame(closeFrameProtocolError)
	CompiledCloseUnsupportedData         = MustCompileFrame(closeFrameUnsupportedData)
	CompiledCloseNoMeaningYet            = MustCompileFrame(closeFrameNoMeaningYet)
	CompiledCloseInvalidFramePayloadData = MustCompileFrame(closeFrameInvalidFramePayloadData)
	CompiledClosePolicyViolation         = MustCompileFrame(closeFramePolicyViolation)
	CompiledCloseMessageTooBig           = MustCompileFrame(closeFrameMessageTooBig)
	CompiledCloseMandatoryExt            = MustCompileFrame(closeFrameMandatoryExt)
	CompiledCloseInternalServerError     = MustCompileFrame(closeFrameInternalServerError)
	CompiledCloseTLSHandshake            = MustCompileFrame(closeFrameTLSHandshake)
)

Compiled control frames for common use cases. For construct-serialize optimizations.

var (
	ErrHeaderLengthMSB        = fmt.Errorf("header error: the most significant bit must be 0")
	ErrHeaderLengthUnexpected = fmt.Errorf("header error: unexpected payload length bits")
)

Errors used by frame reader.

var (
	ErrHandshakeBadProtocol = RejectConnectionError(
		RejectionStatus(http.StatusHTTPVersionNotSupported),
		RejectionReason("handshake error: bad HTTP protocol version"),
	)
	ErrHandshakeBadMethod = RejectConnectionError(
		RejectionStatus(http.StatusMethodNotAllowed),
		RejectionReason("handshake error: bad HTTP request method"),
	)
	ErrHandshakeBadHost = RejectConnectionError(
		RejectionStatus(http.StatusBadRequest),
		RejectionReason(fmt.Sprintf("handshake error: bad %q header", headerHost)),
	)
	ErrHandshakeBadUpgrade = RejectConnectionError(
		RejectionStatus(http.StatusBadRequest),
		RejectionReason(fmt.Sprintf("handshake error: bad %q header", headerUpgrade)),
	)
	ErrHandshakeBadConnection = RejectConnectionError(
		RejectionStatus(http.StatusBadRequest),
		RejectionReason(fmt.Sprintf("handshake error: bad %q header", headerConnection)),
	)
	ErrHandshakeBadSecAccept = RejectConnectionError(
		RejectionStatus(http.StatusBadRequest),
		RejectionReason(fmt.Sprintf("handshake error: bad %q header", headerSecAccept)),
	)
	ErrHandshakeBadSecKey = RejectConnectionError(
		RejectionStatus(http.StatusBadRequest),
		RejectionReason(fmt.Sprintf("handshake error: bad %q header", headerSecKey)),
	)
	ErrHandshakeBadSecVersion = RejectConnectionError(
		RejectionStatus(http.StatusBadRequest),
		RejectionReason(fmt.Sprintf("handshake error: bad %q header", headerSecVersion)),
	)
)

Errors used by both client and server when preparing WebSocket handshake.

var ErrHandshakeUpgradeRequired = RejectConnectionError(
	RejectionStatus(http.StatusUpgradeRequired),
	RejectionHeader(HandshakeHeaderString(headerSecVersion+": 13\r\n")),
	RejectionReason(fmt.Sprintf("handshake error: bad %q header", headerSecVersion)),
)

ErrHandshakeUpgradeRequired is returned by Upgrader to indicate that connection is rejected because given WebSocket version is malformed.

According to RFC6455: If this version does not match a version understood by the server, the server MUST abort the WebSocket handshake described in this section and instead send an appropriate HTTP error code (such as 426 Upgrade Required) and a |Sec-WebSocket-Version| header field indicating the version(s) the server is capable of understanding.

var ErrMalformedRequest = RejectConnectionError(
	RejectionStatus(http.StatusBadRequest),
	RejectionReason("malformed HTTP request"),
)

ErrMalformedRequest is returned when HTTP request can not be parsed.

var ErrMalformedResponse = fmt.Errorf("malformed HTTP response")

ErrMalformedResponse is returned by Dialer to indicate that server response can not be parsed.

var ErrNotHijacker = RejectConnectionError(
	RejectionStatus(http.StatusInternalServerError),
	RejectionReason("given http.ResponseWriter is not a http.Hijacker"),
)

ErrNotHijacker is an error returned when http.ResponseWriter does not implement http.Hijacker interface.

Functions

func CheckCloseFrameData

func CheckCloseFrameData(code StatusCode, reason string) error

CheckCloseFrameData checks received close information to be valid RFC6455 compatible close info.

Note that code.Empty() or code.IsAppLevel() will raise error.

If endpoint sends close frame without status code (with frame.Length = 0), application should not check its payload.

func CheckHeader

func CheckHeader(h Header, s State) error

CheckHeader checks h to contain valid header data for given state s.

Note that zero state (0) means that state is clean, neither server or client side, nor fragmented, nor extended.

func Cipher

func Cipher(payload []byte, mask [4]byte, offset int)

Cipher applies XOR cipher to the payload using mask. Offset is used to cipher chunked data (e.g. in io.Reader implementations).

To convert masked data into unmasked data, or vice versa, the following algorithm is applied. The same algorithm applies regardless of the direction of the translation, e.g., the same steps are applied to mask the data as to unmask the data.

func CompileFrame

func CompileFrame(f Frame) (bts []byte, err error)

CompileFrame returns byte representation of given frame. In terms of memory consumption it is useful to precompile static frames which are often used.

func HeaderSize

func HeaderSize(h Header) (n int)

HeaderSize returns number of bytes that are needed to encode given header. It returns -1 if header is malformed.

func MustCompileFrame

func MustCompileFrame(f Frame) []byte

MustCompileFrame is like CompileFrame but panics if frame can not be encoded.

func MustWriteFrame

func MustWriteFrame(w io.Writer, f Frame)

MustWriteFrame is like WriteFrame but panics if frame can not be read.

func NewCloseFrameBody

func NewCloseFrameBody(code StatusCode, reason string) []byte

NewCloseFrameBody encodes a closure code and a reason into a binary representation.

It returns slice which is at most MaxControlFramePayloadSize bytes length. If the reason is too big it will be cropped to fit the limit defined by the spec.

See https://tools.ietf.org/html/rfc6455#section-5.5

func NewMask

func NewMask() (ret [4]byte)

NewMask creates new random mask.

func PutCloseFrameBody

func PutCloseFrameBody(p []byte, code StatusCode, reason string)

PutCloseFrameBody encodes code and reason into buf.

It will panic if the buffer is too small to accommodate a code or a reason.

PutCloseFrameBody does not check buffer to be RFC compliant, but note that by RFC it must be at most MaxControlFramePayloadSize.

func PutReader

func PutReader(br *bufio.Reader)

PutReader returns bufio.Reader instance to the inner reuse pool. It is useful in rare cases, when Dialer.Dial() returns non-nil buffer which contains unprocessed buffered data, that was sent by the server quickly right after handshake.

func RejectConnectionError

func RejectConnectionError(options ...RejectOption) error

RejectConnectionError constructs an error that could be used to control the way handshake is rejected by Upgrader.

func Rsv

func Rsv(r1, r2, r3 bool) (rsv byte)

Rsv creates rsv byte representation from bits.

func RsvBits

func RsvBits(rsv byte) (r1, r2, r3 bool)

RsvBits returns rsv bits from bytes representation.

func SelectEqual

func SelectEqual(v string) func(string) bool

SelectEqual creates accept function that could be used as Protocol/Extension select during upgrade.

func SelectFromSlice

func SelectFromSlice(accept []string) func(string) bool

SelectFromSlice creates accept function that could be used as Protocol/Extension select during upgrade.

func WriteFrame

func WriteFrame(w io.Writer, f Frame) error

WriteFrame writes frame binary representation into w.

func WriteHeader

func WriteHeader(w io.Writer, h Header) error

WriteHeader writes header binary representation into w.

Types

type ConnectionRejectedError

type ConnectionRejectedError struct {
	// contains filtered or unexported fields
}

ConnectionRejectedError represents a rejection of connection during WebSocket handshake error.

It can be returned by Upgrader's On* hooks to indicate that WebSocket handshake should be rejected.

func (*ConnectionRejectedError) Error

func (r *ConnectionRejectedError) Error() string

Error implements error interface.

func (*ConnectionRejectedError) StatusCode

func (r *ConnectionRejectedError) StatusCode() int

type Dialer

type Dialer struct {
	// ReadBufferSize and WriteBufferSize is an I/O buffer sizes.
	// They used to read and write http data while upgrading to WebSocket.
	// Allocated buffers are pooled with sync.Pool to avoid extra allocations.
	//
	// If a size is zero then default value is used.
	ReadBufferSize, WriteBufferSize int

	// Timeout is the maximum amount of time a Dial() will wait for a connect
	// and an handshake to complete.
	//
	// The default is no timeout.
	Timeout time.Duration

	// Protocols is the list of subprotocols that the client wants to speak,
	// ordered by preference.
	//
	// See https://tools.ietf.org/html/rfc6455#section-4.1
	Protocols []string

	// Extensions is the list of extensions that client wants to speak.
	//
	// Note that if server decides to use some of this extensions, Dial() will
	// return Handshake struct containing a slice of items, which are the
	// shallow copies of the items from this list. That is, internals of
	// Extensions items are shared during Dial().
	//
	// See https://tools.ietf.org/html/rfc6455#section-4.1
	// See https://tools.ietf.org/html/rfc6455#section-9.1
	Extensions []httphead.Option

	// Header is an optional HandshakeHeader instance that could be used to
	// write additional headers to the handshake request.
	//
	// It used instead of any key-value mappings to avoid allocations in user
	// land.
	Header HandshakeHeader

	// Host is an optional string that could be used to specify the host during
	// HTTP upgrade request by setting 'Host' header.
	//
	// Default value is an empty string, which results in setting 'Host' header
	// equal to the URL hostname given to Dialer.Dial().
	Host string

	// OnStatusError is the callback that will be called after receiving non
	// "101 Continue" HTTP response status. It receives an io.Reader object
	// representing server response bytes. That is, it gives ability to parse
	// HTTP response somehow (probably with http.ReadResponse call) and make a
	// decision of further logic.
	//
	// The arguments are only valid until the callback returns.
	OnStatusError func(status int, reason []byte, resp io.Reader)

	// OnHeader is the callback that will be called after successful parsing of
	// header, that is not used during WebSocket handshake procedure. That is,
	// it will be called with non-websocket headers, which could be relevant
	// for application-level logic.
	//
	// The arguments are only valid until the callback returns.
	//
	// Returned value could be used to prevent processing response.
	OnHeader func(key, value []byte) (err error)

	// NetDial is the function that is used to get plain tcp connection.
	// If it is not nil, then it is used instead of net.Dialer.
	NetDial func(ctx context.Context, network, addr string) (net.Conn, error)

	// TLSClient is the callback that will be called after successful dial with
	// received connection and its remote host name. If it is nil, then the
	// default tls.Client() will be used.
	// If it is not nil, then TLSConfig field is ignored.
	TLSClient func(conn net.Conn, hostname string) net.Conn

	// TLSConfig is passed to tls.Client() to start TLS over established
	// connection. If TLSClient is not nil, then it is ignored. If TLSConfig is
	// non-nil and its ServerName is empty, then for every Dial() it will be
	// cloned and appropriate ServerName will be set.
	TLSConfig *tls.Config

	// WrapConn is the optional callback that will be called when connection is
	// ready for an i/o. That is, it will be called after successful dial and
	// TLS initialization (for "wss" schemes). It may be helpful for different
	// user land purposes such as end to end encryption.
	//
	// Note that for debugging purposes of an http handshake (e.g. sent request
	// and received response), there is an wsutil.DebugDialer struct.
	WrapConn func(conn net.Conn) net.Conn
}

Dialer contains options for establishing websocket connection to an url.

var DefaultDialer Dialer

DefaultDialer is dialer that holds no options and is used by Dial function.

func (Dialer) Dial

func (d Dialer) Dial(ctx context.Context, urlstr string) (conn net.Conn, br *bufio.Reader, hs Handshake, err error)

Dial connects to the url host and upgrades connection to WebSocket.

If server has sent frames right after successful handshake then returned buffer will be non-nil. In other cases buffer is always nil. For better memory efficiency received non-nil bufio.Reader should be returned to the inner pool with PutReader() function after use.

Note that Dialer does not implement IDNA (RFC5895) logic as net/http does. If you want to dial non-ascii host name, take care of its name serialization avoiding bad request issues. For more info see net/http Request.Write() implementation, especially cleanHost() function.

func (Dialer) Upgrade

func (d Dialer) Upgrade(conn io.ReadWriter, u *url.URL) (br *bufio.Reader, hs Handshake, err error)

Upgrade writes an upgrade request to the given io.ReadWriter conn at given url u and reads a response from it.

It is a caller responsibility to manage I/O deadlines on conn.

It returns handshake info and some bytes which could be written by the peer right after response and be caught by us during buffered read.

type Frame

type Frame struct {
	Header  Header
	Payload []byte
}

Frame represents websocket frame. See https://tools.ietf.org/html/rfc6455#section-5.2

func MaskFrame

func MaskFrame(f Frame) Frame

MaskFrame masks frame and returns frame with masked payload and Mask header's field set. Note that it copies f payload to prevent collisions. For less allocations you could use MaskFrameInPlace or construct frame manually.

func MaskFrameInPlace

func MaskFrameInPlace(f Frame) Frame

MaskFrameInPlace masks frame and returns frame with masked payload and Mask header's field set. Note that it applies xor cipher to f.Payload without copying, that is, it modifies f.Payload inplace.

func MaskFrameInPlaceWith

func MaskFrameInPlaceWith(f Frame, m [4]byte) Frame

MaskFrameInPlaceWith masks frame with given mask and returns frame with masked payload and Mask header's field set. Note that it applies xor cipher to f.Payload without copying, that is, it modifies f.Payload inplace.

func MaskFrameWith

func MaskFrameWith(f Frame, mask [4]byte) Frame

MaskFrameWith masks frame with given mask and returns frame with masked payload and Mask header's field set. Note that it copies f payload to prevent collisions. For less allocations you could use MaskFrameInPlaceWith or construct frame manually.

func MustReadFrame

func MustReadFrame(r io.Reader) Frame

MustReadFrame is like ReadFrame but panics if frame can not be read.

func NewBinaryFrame

func NewBinaryFrame(p []byte) Frame

NewBinaryFrame creates binary frame with p as payload. Note that p is not copied.

func NewCloseFrame

func NewCloseFrame(p []byte) Frame

NewCloseFrame creates close frame with given close body. Note that p is not copied. Note that p must have length of MaxControlFramePayloadSize bytes or less due to RFC.

func NewFrame

func NewFrame(op OpCode, fin bool, p []byte) Frame

NewFrame creates frame with given operation code, flag of completeness and payload bytes.

func NewPingFrame

func NewPingFrame(p []byte) Frame

NewPingFrame creates ping frame with p as payload. Note that p is not copied. Note that p must have length of MaxControlFramePayloadSize bytes or less due to RFC.

func NewPongFrame

func NewPongFrame(p []byte) Frame

NewPongFrame creates pong frame with p as payload. Note that p is not copied. Note that p must have length of MaxControlFramePayloadSize bytes or less due to RFC.

func NewTextFrame

func NewTextFrame(p []byte) Frame

NewTextFrame creates text frame with p as payload. Note that p is not copied.

func ReadFrame

func ReadFrame(r io.Reader) (f Frame, err error)

ReadFrame reads a frame from r. It is not designed for high optimized use case cause it makes allocation for frame.Header.Length size inside to read frame payload into.

Note that ReadFrame does not unmask payload.

func UnmaskFrame

func UnmaskFrame(f Frame) Frame

UnmaskFrame unmasks frame and returns frame with unmasked payload and Mask header's field cleared. Note that it copies f payload.

func UnmaskFrameInPlace

func UnmaskFrameInPlace(f Frame) Frame

UnmaskFrameInPlace unmasks frame and returns frame with unmasked payload and Mask header's field cleared. Note that it applies xor cipher to f.Payload without copying, that is, it modifies f.Payload inplace.

type HTTPUpgrader

type HTTPUpgrader struct {
	// Timeout is the maximum amount of time an Upgrade() will spent while
	// writing handshake response.
	//
	// The default is no timeout.
	Timeout time.Duration

	// Header is an optional http.Header mapping that could be used to
	// write additional headers to the handshake response.
	//
	// Note that if present, it will be written in any result of handshake.
	Header http.Header

	// Protocol is the select function that is used to select subprotocol from
	// list requested by client. If this field is set, then the first matched
	// protocol is sent to a client as negotiated.
	Protocol func(string) bool

	// Extension is the select function that is used to select extensions from
	// list requested by client. If this field is set, then the all matched
	// extensions are sent to a client as negotiated.
	//
	// Deprecated: use Negotiate instead.
	Extension func(httphead.Option) bool

	// Negotiate is the callback that is used to negotiate extensions from
	// the client's offer. If this field is set, then the returned non-zero
	// extensions are sent to the client as accepted extensions in the
	// response.
	//
	// The argument is only valid until the Negotiate callback returns.
	//
	// If returned error is non-nil then connection is rejected and response is
	// sent with appropriate HTTP error code and body set to error message.
	//
	// RejectConnectionError could be used to get more control on response.
	Negotiate func(httphead.Option) (httphead.Option, error)
}

HTTPUpgrader contains options for upgrading connection to websocket from net/http Handler arguments.

var DefaultHTTPUpgrader HTTPUpgrader

DefaultHTTPUpgrader is an HTTPUpgrader that holds no options and is used by UpgradeHTTP function.

func (HTTPUpgrader) Upgrade

func (u HTTPUpgrader) Upgrade(r *http.Request, w http.ResponseWriter) (conn net.Conn, rw *bufio.ReadWriter, hs Handshake, err error)

Upgrade upgrades http connection to the websocket connection.

It hijacks net.Conn from w and returns received net.Conn and bufio.ReadWriter. On successful handshake it returns Handshake struct describing handshake info.

type Handshake

type Handshake struct {
	// Protocol is the subprotocol selected during handshake.
	Protocol string

	// Extensions is the list of negotiated extensions.
	Extensions []httphead.Option
}

Handshake represents handshake result.

func Dial

func Dial(ctx context.Context, urlstr string) (net.Conn, *bufio.Reader, Handshake, error)

Dial is like Dialer{}.Dial().

func Upgrade

func Upgrade(conn io.ReadWriter) (Handshake, error)

Upgrade is like Upgrader{}.Upgrade().

func UpgradeHTTP

func UpgradeHTTP(r *http.Request, w http.ResponseWriter) (net.Conn, *bufio.ReadWriter, Handshake, error)

UpgradeHTTP is like HTTPUpgrader{}.Upgrade().

type HandshakeHeader

type HandshakeHeader interface {
	io.WriterTo
}

HandshakeHeader is the interface that writes both upgrade request or response headers into a given io.Writer.

type HandshakeHeaderBytes

type HandshakeHeaderBytes []byte

HandshakeHeaderBytes is an adapter to allow the use of headers represented by ordinary slice of bytes as HandshakeHeader.

func (HandshakeHeaderBytes) WriteTo

func (b HandshakeHeaderBytes) WriteTo(w io.Writer) (int64, error)

WriteTo implements HandshakeHeader (and io.WriterTo) interface.

type HandshakeHeaderFunc

type HandshakeHeaderFunc func(io.Writer) (int64, error)

HandshakeHeaderFunc is an adapter to allow the use of headers represented by ordinary function as HandshakeHeader.

func (HandshakeHeaderFunc) WriteTo

func (f HandshakeHeaderFunc) WriteTo(w io.Writer) (int64, error)

WriteTo implements HandshakeHeader (and io.WriterTo) interface.

type HandshakeHeaderHTTP

type HandshakeHeaderHTTP http.Header

HandshakeHeaderHTTP is an adapter to allow the use of http.Header as HandshakeHeader.

func (HandshakeHeaderHTTP) WriteTo

func (h HandshakeHeaderHTTP) WriteTo(w io.Writer) (int64, error)

WriteTo implements HandshakeHeader (and io.WriterTo) interface.

type HandshakeHeaderString

type HandshakeHeaderString string

HandshakeHeaderString is an adapter to allow the use of headers represented by ordinary string as HandshakeHeader.

func (HandshakeHeaderString) WriteTo

func (s HandshakeHeaderString) WriteTo(w io.Writer) (int64, error)

WriteTo implements HandshakeHeader (and io.WriterTo) interface.

type Header

type Header struct {
	Fin    bool
	Rsv    byte
	OpCode OpCode
	Masked bool
	Mask   [4]byte
	Length int64
}

Header represents websocket frame header. See https://tools.ietf.org/html/rfc6455#section-5.2

func ReadHeader

func ReadHeader(r io.Reader) (h Header, err error)

ReadHeader reads a frame header from r.

func (Header) Rsv1

func (h Header) Rsv1() bool

Rsv1 reports whether the header has first rsv bit set.

func (Header) Rsv2

func (h Header) Rsv2() bool

Rsv2 reports whether the header has second rsv bit set.

func (Header) Rsv3

func (h Header) Rsv3() bool

Rsv3 reports whether the header has third rsv bit set.

type OpCode

type OpCode byte

OpCode represents operation code.

const (
	OpContinuation OpCode = 0x0
	OpText         OpCode = 0x1
	OpBinary       OpCode = 0x2
	OpClose        OpCode = 0x8
	OpPing         OpCode = 0x9
	OpPong         OpCode = 0xa
)

Operation codes defined by specification. See https://tools.ietf.org/html/rfc6455#section-5.2

func (OpCode) IsControl

func (c OpCode) IsControl() bool

IsControl checks whether the c is control operation code. See https://tools.ietf.org/html/rfc6455#section-5.5

func (OpCode) IsData

func (c OpCode) IsData() bool

IsData checks whether the c is data operation code. See https://tools.ietf.org/html/rfc6455#section-5.6

func (OpCode) IsReserved

func (c OpCode) IsReserved() bool

IsReserved checks whether the c is reserved operation code. See https://tools.ietf.org/html/rfc6455#section-5.2

type ProtocolError

type ProtocolError string

ProtocolError describes error during checking/parsing websocket frames or headers.

func (ProtocolError) Error

func (p ProtocolError) Error() string

Error implements error interface.

type RejectOption

type RejectOption func(*ConnectionRejectedError)

RejectOption represents an option used to control the way connection is rejected.

func RejectionHeader

func RejectionHeader(h HandshakeHeader) RejectOption

RejectionHeader returns an option that makes connection to be rejected with given HTTP headers.

func RejectionReason

func RejectionReason(reason string) RejectOption

RejectionReason returns an option that makes connection to be rejected with given reason.

func RejectionStatus

func RejectionStatus(code int) RejectOption

RejectionStatus returns an option that makes connection to be rejected with given HTTP status code.

type State

type State uint8

State represents state of websocket endpoint. It used by some functions to be more strict when checking compatibility with RFC6455.

const (
	// StateServerSide means that endpoint (caller) is a server.
	StateServerSide State = 0x1 << iota
	// StateClientSide means that endpoint (caller) is a client.
	StateClientSide
	// StateExtended means that extension was negotiated during handshake.
	StateExtended
	// StateFragmented means that endpoint (caller) has received fragmented
	// frame and waits for continuation parts.
	StateFragmented
)

func (State) Clear

func (s State) Clear(v State) State

Clear disables v state on s.

func (State) ClientSide

func (s State) ClientSide() bool

ClientSide reports whether state represents client side.

func (State) Extended

func (s State) Extended() bool

Extended reports whether state is extended.

func (State) Fragmented

func (s State) Fragmented() bool

Fragmented reports whether state is fragmented.

func (State) Is

func (s State) Is(v State) bool

Is checks whether the s has v enabled.

func (State) ServerSide

func (s State) ServerSide() bool

ServerSide reports whether states represents server side.

func (State) Set

func (s State) Set(v State) State

Set enables v state on s.

type StatusCode

type StatusCode uint16

StatusCode represents the encoded reason for closure of websocket connection.

There are few helper methods on StatusCode that helps to define a range in which given code is lay in. accordingly to ranges defined in specification.

See https://tools.ietf.org/html/rfc6455#section-7.4

const (
	StatusNormalClosure           StatusCode = 1000
	StatusGoingAway               StatusCode = 1001
	StatusProtocolError           StatusCode = 1002
	StatusUnsupportedData         StatusCode = 1003
	StatusNoMeaningYet            StatusCode = 1004
	StatusInvalidFramePayloadData StatusCode = 1007
	StatusPolicyViolation         StatusCode = 1008
	StatusMessageTooBig           StatusCode = 1009
	StatusMandatoryExt            StatusCode = 1010
	StatusInternalServerError     StatusCode = 1011
	StatusTLSHandshake            StatusCode = 1015

	// StatusAbnormalClosure is a special code designated for use in
	// applications.
	StatusAbnormalClosure StatusCode = 1006

	// StatusNoStatusRcvd is a special code designated for use in applications.
	StatusNoStatusRcvd StatusCode = 1005
)

Status codes defined by specification. See https://tools.ietf.org/html/rfc6455#section-7.4.1

func ParseCloseFrameData

func ParseCloseFrameData(payload []byte) (code StatusCode, reason string)

ParseCloseFrameData parses close frame status code and closure reason if any provided. If there is no status code in the payload the empty status code is returned (code.Empty()) with empty string as a reason.

func ParseCloseFrameDataUnsafe

func ParseCloseFrameDataUnsafe(payload []byte) (code StatusCode, reason string)

ParseCloseFrameDataUnsafe is like ParseCloseFrameData except the thing that it does not copies payload bytes into reason, but prepares unsafe cast.

func (StatusCode) Empty

func (s StatusCode) Empty() bool

Empty reports whether the code is empty. Empty code has no any meaning neither app level codes nor other. This method is useful just to check that code is golang default value 0.

func (StatusCode) In

func (s StatusCode) In(r StatusCodeRange) bool

In reports whether the code is defined in given range.

func (StatusCode) IsApplicationSpec

func (s StatusCode) IsApplicationSpec() bool

IsApplicationSpec reports whether the code should be defined by application, framework or libraries specification.

func (StatusCode) IsNotUsed

func (s StatusCode) IsNotUsed() bool

IsNotUsed reports whether the code is predefined in not used range.

func (StatusCode) IsPrivateSpec

func (s StatusCode) IsPrivateSpec() bool

IsPrivateSpec reports whether the code should be defined privately.

func (StatusCode) IsProtocolDefined

func (s StatusCode) IsProtocolDefined() bool

IsProtocolDefined reports whether the code is already defined by protocol specification.

func (StatusCode) IsProtocolReserved

func (s StatusCode) IsProtocolReserved() bool

IsProtocolReserved reports whether the code is defined by protocol specification to be reserved only for application usage purpose.

func (StatusCode) IsProtocolSpec

func (s StatusCode) IsProtocolSpec() bool

IsProtocolSpec reports whether the code should be defined by protocol specification.

type StatusCodeRange

type StatusCodeRange struct {
	Min, Max StatusCode
}

StatusCodeRange describes range of StatusCode values.

type StatusError

type StatusError int

StatusError contains an unexpected status-line code from the server.

func (StatusError) Error

func (s StatusError) Error() string

type Upgrader

type Upgrader struct {
	// ReadBufferSize and WriteBufferSize is an I/O buffer sizes.
	// They used to read and write http data while upgrading to WebSocket.
	// Allocated buffers are pooled with sync.Pool to avoid extra allocations.
	//
	// If a size is zero then default value is used.
	//
	// Usually it is useful to set read buffer size bigger than write buffer
	// size because incoming request could contain long header values, such as
	// Cookie. Response, in other way, could be big only if user write multiple
	// custom headers. Usually response takes less than 256 bytes.
	ReadBufferSize, WriteBufferSize int

	// Protocol is a select function that is used to select subprotocol
	// from list requested by client. If this field is set, then the first matched
	// protocol is sent to a client as negotiated.
	//
	// The argument is only valid until the callback returns.
	Protocol func([]byte) bool

	// ProtocolCustrom allow user to parse Sec-WebSocket-Protocol header manually.
	// Note that returned bytes must be valid until Upgrade returns.
	// If ProtocolCustom is set, it used instead of Protocol function.
	ProtocolCustom func([]byte) (string, bool)

	// Extension is a select function that is used to select extensions
	// from list requested by client. If this field is set, then the all matched
	// extensions are sent to a client as negotiated.
	//
	// Note that Extension may be called multiple times and implementations
	// must track uniqueness of accepted extensions manually.
	//
	// The argument is only valid until the callback returns.
	//
	// According to the RFC6455 order of extensions passed by a client is
	// significant. That is, returning true from this function means that no
	// other extension with the same name should be checked because server
	// accepted the most preferable extension right now:
	// "Note that the order of extensions is significant.  Any interactions between
	// multiple extensions MAY be defined in the documents defining the extensions.
	// In the absence of such definitions, the interpretation is that the header
	// fields listed by the client in its request represent a preference of the
	// header fields it wishes to use, with the first options listed being most
	// preferable."
	//
	// Deprecated: use Negotiate instead.
	Extension func(httphead.Option) bool

	// ExtensionCustom allow user to parse Sec-WebSocket-Extensions header
	// manually.
	//
	// If ExtensionCustom() decides to accept received extension, it must
	// append appropriate option to the given slice of httphead.Option.
	// It returns results of append() to the given slice and a flag that
	// reports whether given header value is wellformed or not.
	//
	// Note that ExtensionCustom may be called multiple times and
	// implementations must track uniqueness of accepted extensions manually.
	//
	// Note that returned options should be valid until Upgrade returns.
	// If ExtensionCustom is set, it used instead of Extension function.
	ExtensionCustom func([]byte, []httphead.Option) ([]httphead.Option, bool)

	// Negotiate is the callback that is used to negotiate extensions from
	// the client's offer. If this field is set, then the returned non-zero
	// extensions are sent to the client as accepted extensions in the
	// response.
	//
	// The argument is only valid until the Negotiate callback returns.
	//
	// If returned error is non-nil then connection is rejected and response is
	// sent with appropriate HTTP error code and body set to error message.
	//
	// RejectConnectionError could be used to get more control on response.
	Negotiate func(httphead.Option) (httphead.Option, error)

	// Header is an optional HandshakeHeader instance that could be used to
	// write additional headers to the handshake response.
	//
	// It used instead of any key-value mappings to avoid allocations in user
	// land.
	//
	// Note that if present, it will be written in any result of handshake.
	Header HandshakeHeader

	// OnRequest is a callback that will be called after request line
	// successful parsing.
	//
	// The arguments are only valid until the callback returns.
	//
	// If returned error is non-nil then connection is rejected and response is
	// sent with appropriate HTTP error code and body set to error message.
	//
	// RejectConnectionError could be used to get more control on response.
	OnRequest func(uri []byte) error

	// OnHost is a callback that will be called after "Host" header successful
	// parsing.
	//
	// It is separated from OnHeader callback because the Host header must be
	// present in each request since HTTP/1.1. Thus Host header is non-optional
	// and required for every WebSocket handshake.
	//
	// The arguments are only valid until the callback returns.
	//
	// If returned error is non-nil then connection is rejected and response is
	// sent with appropriate HTTP error code and body set to error message.
	//
	// RejectConnectionError could be used to get more control on response.
	OnHost func(host []byte) error

	// OnHeader is a callback that will be called after successful parsing of
	// header, that is not used during WebSocket handshake procedure. That is,
	// it will be called with non-websocket headers, which could be relevant
	// for application-level logic.
	//
	// The arguments are only valid until the callback returns.
	//
	// If returned error is non-nil then connection is rejected and response is
	// sent with appropriate HTTP error code and body set to error message.
	//
	// RejectConnectionError could be used to get more control on response.
	OnHeader func(key, value []byte) error

	// OnBeforeUpgrade is a callback that will be called before sending
	// successful upgrade response.
	//
	// Setting OnBeforeUpgrade allows user to make final application-level
	// checks and decide whether this connection is allowed to successfully
	// upgrade to WebSocket.
	//
	// It must return non-nil either HandshakeHeader or error and never both.
	//
	// If returned error is non-nil then connection is rejected and response is
	// sent with appropriate HTTP error code and body set to error message.
	//
	// RejectConnectionError could be used to get more control on response.
	OnBeforeUpgrade func() (header HandshakeHeader, err error)
}

Upgrader contains options for upgrading connection to websocket.

var DefaultUpgrader Upgrader

DefaultUpgrader is an Upgrader that holds no options and is used by Upgrade function.

func (Upgrader) Upgrade

func (u Upgrader) Upgrade(conn io.ReadWriter) (hs Handshake, err error)

Upgrade zero-copy upgrades connection to WebSocket. It interprets given conn as connection with incoming HTTP Upgrade request.

It is a caller responsibility to manage i/o timeouts on conn.

Non-nil error means that request for the WebSocket upgrade is invalid or malformed and usually connection should be closed. Even when error is non-nil Upgrade will write appropriate response into connection in compliance with RFC.