websocket

README

Gorilla WebSocket

Gorilla WebSocket is a Go implementation of the WebSocket protocol.

Documentation

• API Reference
• Chat example
• Command example
• Client and server example
• File watch example

Status

The Gorilla WebSocket package provides a complete and tested implementation of the WebSocket protocol. The package API is stable.

Installation

go get github.com/gorilla/websocket

Protocol Compliance

The Gorilla WebSocket package passes the server tests in the Autobahn Test Suite using the application in the examples/autobahn subdirectory.

Gorilla WebSocket compared with other packages

	github.com/gorilla	golang.org/x/net
RFC 6455 Features
Passes Autobahn Test Suite	Yes	No
Receive fragmented message	Yes	No, see note 1
Send close message	Yes	No
Send pings and receive pongs	Yes	No
Get the type of a received data message	Yes	Yes, see note 2
Other Features
Limit size of received message	Yes	No
Read message using io.Reader	Yes	No, see note 3
Write message using io.WriteCloser	Yes	No, see note 3

Notes:

1. Large messages are fragmented in Chrome's new WebSocket implementation.
2. The application can get the type of a received data message by implementing a Codec marshal function.
3. The go.net io.Reader and io.Writer operate across WebSocket frame boundaries. Read returns when the input buffer is full or a frame boundary is encountered. Each call to Write sends a single frame message. The Gorilla io.Reader and io.WriteCloser operate on a single WebSocket message.

Documentation

Overview

Package websocket implements the WebSocket protocol defined in RFC 6455.

Overview

The Conn type represents a WebSocket connection. A server application uses the Upgrade function from an Upgrader object with a HTTP request handler to get a pointer to a Conn:

var upgrader = websocket.Upgrader{
    ReadBufferSize:  1024,
    WriteBufferSize: 1024,
}

func handler(w http.ResponseWriter, r *http.Request) {
    conn, err := upgrader.Upgrade(w, r, nil)
    if err != nil {
        log.Println(err)
        return
    }
    ... Use conn to send and receive messages.
}

Call the connection's WriteMessage and ReadMessage methods to send and receive messages as a slice of bytes. This snippet of code shows how to echo messages using these methods:

for {
    messageType, p, err := conn.ReadMessage()
    if err != nil {
        return
    }
    if err = conn.WriteMessage(messageType, p); err != nil {
        return err
    }
}

In above snippet of code, p is a []byte and messageType is an int with value websocket.BinaryMessage or websocket.TextMessage.

An application can also send and receive messages using the io.WriteCloser and io.Reader interfaces. To send a message, call the connection NextWriter method to get an io.WriteCloser, write the message to the writer and close the writer when done. To receive a message, call the connection NextReader method to get an io.Reader and read until io.EOF is returned. This snippet snippet shows how to echo messages using the NextWriter and NextReader methods:

for {
    messageType, r, err := conn.NextReader()
    if err != nil {
        return
    }
    w, err := conn.NextWriter(messageType)
    if err != nil {
        return err
    }
    if _, err := io.Copy(w, r); err != nil {
        return err
    }
    if err := w.Close(); err != nil {
        return err
    }
}

Data Messages

The WebSocket protocol distinguishes between text and binary data messages. Text messages are interpreted as UTF-8 encoded text. The interpretation of binary messages is left to the application.

This package uses the TextMessage and BinaryMessage integer constants to identify the two data message types. The ReadMessage and NextReader methods return the type of the received message. The messageType argument to the WriteMessage and NextWriter methods specifies the type of a sent message.

It is the application's responsibility to ensure that text messages are valid UTF-8 encoded text.

Control Messages

The WebSocket protocol defines three types of control messages: close, ping and pong. Call the connection WriteControl, WriteMessage or NextWriter methods to send a control message to the peer.

Connections handle received ping and pong messages by invoking a callback function set with SetPingHandler and SetPongHandler methods. These callback functions can be invoked from the ReadMessage method, the NextReader method or from a call to the data message reader returned from NextReader.

Connections handle received close messages by returning an error from the ReadMessage method, the NextReader method or from a call to the data message reader returned from NextReader.

Concurrency

Connections support one concurrent reader and one concurrent writer.

Applications are responsible for ensuring that no more than one goroutine calls the write methods (NextWriter, SetWriteDeadline, WriteMessage, WriteJSON) concurrently and that no more than one goroutine calls the read methods (NextReader, SetReadDeadline, ReadMessage, ReadJSON, SetPongHandler, SetPingHandler) concurrently.

The Close and WriteControl methods can be called concurrently with all other methods.

Read is Required

The application must read the connection to process ping and close messages sent from the peer. If the application is not otherwise interested in messages from the peer, then the application should start a goroutine to read and discard messages from the peer. A simple example is:

func readLoop(c *websocket.Conn) {
    for {
        if _, _, err := c.NextReader(); err != nil {
            c.Close()
            break
        }
    }
}

Origin Considerations

Web browsers allow Javascript applications to open a WebSocket connection to any host. It's up to the server to enforce an origin policy using the Origin request header sent by the browser.

The Upgrader calls the function specified in the CheckOrigin field to check the origin. If the CheckOrigin function returns false, then the Upgrade method fails the WebSocket handshake with HTTP status 403.

If the CheckOrigin field is nil, then the Upgrader uses a safe default: fail the handshake if the Origin request header is present and not equal to the Host request header.

An application can allow connections from any origin by specifying a function that always returns true:

 var upgrader = websocket.Upgrader{
   CheckOrigin: func(r *http.Request) bool { return true },
}

The deprecated Upgrade function does not enforce an origin policy. It's the application's responsibility to check the Origin header before calling Upgrade.

Index

• Constants
• Variables
• func FormatCloseMessage(closeCode int, text string) []byte
• func ReadJSON(c *Conn, v interface{}) error
• func Subprotocols(r *http.Request) []string
• func WriteJSON(c *Conn, v interface{}) error
• type CloseError
  • func (e *CloseError) Error() string
• type Conn
  • func NewClient(netConn net.Conn, u *url.URL, requestHeader http.Header, ...) (c *Conn, response *http.Response, err error)
  • func Upgrade(w http.ResponseWriter, r *http.Request, responseHeader http.Header, ...) (*Conn, error)
  • func (c *Conn) Close() error
  • func (c *Conn) LocalAddr() net.Addr
  • func (c *Conn) NextReader() (messageType int, r io.Reader, err error)
  • func (c *Conn) NextWriter(messageType int) (io.WriteCloser, error)
  • func (c *Conn) ReadJSON(v interface{}) error
  • func (c *Conn) ReadMessage() (messageType int, p []byte, err error)
  • func (c *Conn) RemoteAddr() net.Addr
  • func (c *Conn) SetPingHandler(h func(appData string) error)
  • func (c *Conn) SetPongHandler(h func(appData string) error)
  • func (c *Conn) SetReadDeadline(t time.Time) error
  • func (c *Conn) SetReadLimit(limit int64)
  • func (c *Conn) SetWriteDeadline(t time.Time) error
  • func (c *Conn) Subprotocol() string
  • func (c *Conn) UnderlyingConn() net.Conn
  • func (c *Conn) WriteControl(messageType int, data []byte, deadline time.Time) error
  • func (c *Conn) WriteJSON(v interface{}) error
  • func (c *Conn) WriteMessage(messageType int, data []byte) error
• type Dialer
  • func (d *Dialer) Dial(urlStr string, requestHeader http.Header) (*Conn, *http.Response, error)
• type HandshakeError
  • func (e HandshakeError) Error() string
• type Upgrader
  • func (u *Upgrader) Upgrade(w http.ResponseWriter, r *http.Request, responseHeader http.Header) (*Conn, error)

Constants

const (
	CloseNormalClosure           = 1000
	CloseGoingAway               = 1001
	CloseProtocolError           = 1002
	CloseUnsupportedData         = 1003
	CloseNoStatusReceived        = 1005
	CloseAbnormalClosure         = 1006
	CloseInvalidFramePayloadData = 1007
	ClosePolicyViolation         = 1008
	CloseMessageTooBig           = 1009
	CloseMandatoryExtension      = 1010
	CloseInternalServerErr       = 1011
	CloseTLSHandshake            = 1015
)

Close codes defined in RFC 6455, section 11.7.

const (
	// TextMessage denotes a text data message. The text message payload is
	// interpreted as UTF-8 encoded text data.
	TextMessage = 1

	// BinaryMessage denotes a binary data message.
	BinaryMessage = 2

	// CloseMessage denotes a close control message. The optional message
	// payload contains a numeric code and text. Use the FormatCloseMessage
	// function to format a close message payload.
	CloseMessage = 8

	// PingMessage denotes a ping control message. The optional message payload
	// is UTF-8 encoded text.
	PingMessage = 9

	// PongMessage denotes a ping control message. The optional message payload
	// is UTF-8 encoded text.
	PongMessage = 10
)

The message types are defined in RFC 6455, section 11.8.

Variables

var DefaultDialer = &Dialer{
	Proxy: http.ProxyFromEnvironment,
}

DefaultDialer is a dialer with all fields set to the default zero values.

var ErrBadHandshake = errors.New("websocket: bad handshake")

ErrBadHandshake is returned when the server response to opening handshake is invalid.

var ErrCloseSent = errors.New("websocket: close sent")

ErrCloseSent is returned when the application writes a message to the connection after sending a close message.

var ErrReadLimit = errors.New("websocket: read limit exceeded")

ErrReadLimit is returned when reading a message that is larger than the read limit set for the connection.

Functions

func FormatCloseMessage

func FormatCloseMessage(closeCode int, text string) []byte

FormatCloseMessage formats closeCode and text as a WebSocket close message.

func ReadJSON

func ReadJSON(c *Conn, v interface{}) error

ReadJSON is deprecated, use c.ReadJSON instead.

func Subprotocols

func Subprotocols(r *http.Request) []string

Subprotocols returns the subprotocols requested by the client in the Sec-Websocket-Protocol header.

func WriteJSON

func WriteJSON(c *Conn, v interface{}) error

WriteJSON is deprecated, use c.WriteJSON instead.

Types

type CloseError

type CloseError struct {

	// Code is defined in RFC 6455, section 11.7.
	Code int

	// Text is the optional text payload.
	Text string
}

CloseError represents close frame.

func (*CloseError) Error

func (e *CloseError) Error() string

type Conn

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

Conn represents a WebSocket connection.

func NewClient

func NewClient(netConn net.Conn, u *url.URL, requestHeader http.Header, readBufSize, writeBufSize int) (c *Conn, response *http.Response, err error)

NewClient creates a new client connection using the given net connection. The URL u specifies the host and request URI. Use requestHeader to specify the origin (Origin), subprotocols (Sec-WebSocket-Protocol) and cookies (Cookie). Use the response.Header to get the selected subprotocol (Sec-WebSocket-Protocol) and cookies (Set-Cookie).

If the WebSocket handshake fails, ErrBadHandshake is returned along with a non-nil *http.Response so that callers can handle redirects, authentication, etc.

Deprecated: Use Dialer instead.

func Upgrade

func Upgrade(w http.ResponseWriter, r *http.Request, responseHeader http.Header, readBufSize, writeBufSize int) (*Conn, error)

Upgrade upgrades the HTTP server connection to the WebSocket protocol.

This function is deprecated, use websocket.Upgrader instead.

The application is responsible for checking the request origin before calling Upgrade. An example implementation of the same origin policy is:

if req.Header.Get("Origin") != "http://"+req.Host {
	http.Error(w, "Origin not allowed", 403)
	return
}

If the endpoint supports subprotocols, then the application is responsible for negotiating the protocol used on the connection. Use the Subprotocols() function to get the subprotocols requested by the client. Use the Sec-Websocket-Protocol response header to specify the subprotocol selected by the application.

The responseHeader is included in the response to the client's upgrade request. Use the responseHeader to specify cookies (Set-Cookie) and the negotiated subprotocol (Sec-Websocket-Protocol).

The connection buffers IO to the underlying network connection. The readBufSize and writeBufSize parameters specify the size of the buffers to use. Messages can be larger than the buffers.

If the request is not a valid WebSocket handshake, then Upgrade returns an error of type HandshakeError. Applications should handle this error by replying to the client with an HTTP error response.

func (*Conn) Close

func (c *Conn) Close() error

Close closes the underlying network connection without sending or waiting for a close frame.

func (*Conn) LocalAddr

func (c *Conn) LocalAddr() net.Addr

LocalAddr returns the local network address.

func (*Conn) NextReader

func (c *Conn) NextReader() (messageType int, r io.Reader, err error)

NextReader returns the next data message received from the peer. The returned messageType is either TextMessage or BinaryMessage.

There can be at most one open reader on a connection. NextReader discards the previous message if the application has not already consumed it.

The NextReader method and the readers returned from the method cannot be accessed by more than one goroutine at a time.

func (*Conn) NextWriter

func (c *Conn) NextWriter(messageType int) (io.WriteCloser, error)

NextWriter returns a writer for the next message to send. The writer's Close method flushes the complete message to the network.

There can be at most one open writer on a connection. NextWriter closes the previous writer if the application has not already done so.

The NextWriter method and the writers returned from the method cannot be accessed by more than one goroutine at a time.

func (*Conn) ReadJSON

func (c *Conn) ReadJSON(v interface{}) error

ReadJSON reads the next JSON-encoded message from the connection and stores it in the value pointed to by v.

See the documentation for the encoding/json Unmarshal function for details about the conversion of JSON to a Go value.

func (*Conn) ReadMessage

func (c *Conn) ReadMessage() (messageType int, p []byte, err error)

ReadMessage is a helper method for getting a reader using NextReader and reading from that reader to a buffer.

func (*Conn) RemoteAddr

func (c *Conn) RemoteAddr() net.Addr

RemoteAddr returns the remote network address.

func (*Conn) SetPingHandler

func (c *Conn) SetPingHandler(h func(appData string) error)

SetPingHandler sets the handler for ping messages received from the peer. The appData argument to h is the PING frame application data. The default ping handler sends a pong to the peer.

func (*Conn) SetPongHandler

func (c *Conn) SetPongHandler(h func(appData string) error)

SetPongHandler sets the handler for pong messages received from the peer. The appData argument to h is the PONG frame application data. The default pong handler does nothing.

func (*Conn) SetReadDeadline

func (c *Conn) SetReadDeadline(t time.Time) error

SetReadDeadline sets the read deadline on the underlying network connection. After a read has timed out, the websocket connection state is corrupt and all future reads will return an error. A zero value for t means reads will not time out.

func (*Conn) SetReadLimit

func (c *Conn) SetReadLimit(limit int64)

SetReadLimit sets the maximum size for a message read from the peer. If a message exceeds the limit, the connection sends a close frame to the peer and returns ErrReadLimit to the application.

func (*Conn) SetWriteDeadline

func (c *Conn) SetWriteDeadline(t time.Time) error

SetWriteDeadline sets the write deadline on the underlying network connection. After a write has timed out, the websocket state is corrupt and all future writes will return an error. A zero value for t means writes will not time out.

func (*Conn) Subprotocol

func (c *Conn) Subprotocol() string

Subprotocol returns the negotiated protocol for the connection.

func (*Conn) UnderlyingConn

func (c *Conn) UnderlyingConn() net.Conn

UnderlyingConn returns the internal net.Conn. This can be used to further modifications to connection specific flags.

func (*Conn) WriteControl

func (c *Conn) WriteControl(messageType int, data []byte, deadline time.Time) error

WriteControl writes a control message with the given deadline. The allowed message types are CloseMessage, PingMessage and PongMessage.

func (*Conn) WriteJSON

func (c *Conn) WriteJSON(v interface{}) error

WriteJSON writes the JSON encoding of v to the connection.

See the documentation for encoding/json Marshal for details about the conversion of Go values to JSON.

func (*Conn) WriteMessage

func (c *Conn) WriteMessage(messageType int, data []byte) error

WriteMessage is a helper method for getting a writer using NextWriter, writing the message and closing the writer.

type Dialer

type Dialer struct {
	// NetDial specifies the dial function for creating TCP connections. If
	// NetDial is nil, net.Dial is used.
	NetDial func(network, addr string) (net.Conn, error)

	// Proxy specifies a function to return a proxy for a given
	// Request. If the function returns a non-nil error, the
	// request is aborted with the provided error.
	// If Proxy is nil or returns a nil *URL, no proxy is used.
	Proxy func(*http.Request) (*url.URL, error)

	// TLSClientConfig specifies the TLS configuration to use with tls.Client.
	// If nil, the default configuration is used.
	TLSClientConfig *tls.Config

	// HandshakeTimeout specifies the duration for the handshake to complete.
	HandshakeTimeout time.Duration

	// Input and output buffer sizes. If the buffer size is zero, then a
	// default value of 4096 is used.
	ReadBufferSize, WriteBufferSize int

	// Subprotocols specifies the client's requested subprotocols.
	Subprotocols []string
}

A Dialer contains options for connecting to WebSocket server.

func (*Dialer) Dial

func (d *Dialer) Dial(urlStr string, requestHeader http.Header) (*Conn, *http.Response, error)

Dial creates a new client connection. Use requestHeader to specify the origin (Origin), subprotocols (Sec-WebSocket-Protocol) and cookies (Cookie). Use the response.Header to get the selected subprotocol (Sec-WebSocket-Protocol) and cookies (Set-Cookie).

If the WebSocket handshake fails, ErrBadHandshake is returned along with a non-nil *http.Response so that callers can handle redirects, authentication, etcetera. The response body may not contain the entire response and does not need to be closed by the application.

type HandshakeError

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

HandshakeError describes an error with the handshake from the peer.

func (HandshakeError) Error

func (e HandshakeError) Error() string

type Upgrader

type Upgrader struct {
	// HandshakeTimeout specifies the duration for the handshake to complete.
	HandshakeTimeout time.Duration

	// ReadBufferSize and WriteBufferSize specify I/O buffer sizes. If a buffer
	// size is zero, then a default value of 4096 is used. The I/O buffer sizes
	// do not limit the size of the messages that can be sent or received.
	ReadBufferSize, WriteBufferSize int

	// Subprotocols specifies the server's supported protocols in order of
	// preference. If this field is set, then the Upgrade method negotiates a
	// subprotocol by selecting the first match in this list with a protocol
	// requested by the client.
	Subprotocols []string

	// Error specifies the function for generating HTTP error responses. If Error
	// is nil, then http.Error is used to generate the HTTP response.
	Error func(w http.ResponseWriter, r *http.Request, status int, reason error)

	// CheckOrigin returns true if the request Origin header is acceptable. If
	// CheckOrigin is nil, the host in the Origin header must not be set or
	// must match the host of the request.
	CheckOrigin func(r *http.Request) bool
}

Upgrader specifies parameters for upgrading an HTTP connection to a WebSocket connection.

func (*Upgrader) Upgrade

func (u *Upgrader) Upgrade(w http.ResponseWriter, r *http.Request, responseHeader http.Header) (*Conn, error)

Upgrade upgrades the HTTP server connection to the WebSocket protocol.

The responseHeader is included in the response to the client's upgrade request. Use the responseHeader to specify cookies (Set-Cookie) and the application negotiated subprotocol (Sec-Websocket-Protocol).