Documentation ¶
Overview ¶
Package websocket is a minimal and idiomatic implementation of the WebSocket protocol.
https://tools.ietf.org/html/rfc6455
Conn, Dial, and Accept are the main entrypoints into this package. Use Dial to dial a WebSocket server, Accept to accept a WebSocket client dial and then Conn to interact with the resulting WebSocket connections.
The examples are the best way to understand how to correctly use the library.
The wsjson and wspb subpackages contain helpers for JSON and ProtoBuf messages.
See https://nhooyr.io/websocket for more overview docs and a comparison with existing implementations.
Use the errors.As function new in Go 1.13 to check for websocket.CloseError. Or use the CloseStatus function to grab the StatusCode out of a websocket.CloseError See the CloseStatus example.
Wasm ¶
The client side fully supports compiling to Wasm. It wraps the WebSocket browser API.
See https://developer.mozilla.org/en-US/docs/Web/API/WebSocket
Thus the unsupported features (not compiled in) for Wasm are:
- Accept and AcceptOptions
- Conn.Ping
- HTTPClient and HTTPHeader fields in DialOptions
The *http.Response returned by Dial will always either be nil or &http.Response{} as we do not have access to the handshake response in the browser.
The Writer method on the Conn buffers everything in memory and then sends it as a message when the writer is closed.
The Reader method also reads the entire response and then returns a reader that reads from the byte slice.
SetReadLimit cannot actually limit the number of bytes read from the connection so instead when a message beyond the limit is fully read, it throws an error.
Writes are also always async so the passed context is no-op.
Everything else is fully supported. This includes the wsjson and wspb helper packages.
Once https://github.com/gopherjs/gopherjs/issues/929 is closed, GopherJS should be supported as well.
Example (Echo) ¶
This example starts a WebSocket echo server, dials the server and then sends 5 different messages and prints out the server's responses.
//go:build !js // +build !js package main import ( "context" "fmt" "io" "log" "net" "net/http" "time" "golang.org/x/time/rate" "nhooyr.io/websocket" "nhooyr.io/websocket/wsjson" ) // This example starts a WebSocket echo server, // dials the server and then sends 5 different messages // and prints out the server's responses. func main() { // First we listen on port 0 which means the OS will // assign us a random free port. This is the listener // the server will serve on and the client will connect to. l, err := net.Listen("tcp", "localhost:0") if err != nil { log.Fatalf("failed to listen: %v", err) } defer l.Close() s := &http.Server{ Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { err := echoServer(w, r) if err != nil { log.Printf("echo server: %v", err) } }), ReadTimeout: time.Second * 15, WriteTimeout: time.Second * 15, } defer s.Close() // This starts the echo server on the listener. go func() { err := s.Serve(l) if err != http.ErrServerClosed { log.Fatalf("failed to listen and serve: %v", err) } }() // Now we dial the server, send the messages and echo the responses. err = client("ws://" + l.Addr().String()) if err != nil { log.Fatalf("client failed: %v", err) } } // echoServer is the WebSocket echo server implementation. // It ensures the client speaks the echo subprotocol and // only allows one message every 100ms with a 10 message burst. func echoServer(w http.ResponseWriter, r *http.Request) error { c, err := websocket.Accept(w, r, &websocket.AcceptOptions{ Subprotocols: []string{"echo"}, }) if err != nil { return err } defer c.Close(websocket.StatusInternalError, "the sky is falling") if c.Subprotocol() != "echo" { c.Close(websocket.StatusPolicyViolation, "client must speak the echo subprotocol") return fmt.Errorf("client does not speak echo sub protocol") } l := rate.NewLimiter(rate.Every(time.Millisecond*100), 10) for { err = echo(r.Context(), c, l) if websocket.CloseStatus(err) == websocket.StatusNormalClosure { return nil } if err != nil { return fmt.Errorf("failed to echo with %v: %w", r.RemoteAddr, err) } } } // echo reads from the websocket connection and then writes // the received message back to it. // The entire function has 10s to complete. func echo(ctx context.Context, c *websocket.Conn, l *rate.Limiter) error { ctx, cancel := context.WithTimeout(ctx, time.Second*10) defer cancel() err := l.Wait(ctx) if err != nil { return err } typ, r, err := c.Reader(ctx) if err != nil { return err } w, err := c.Writer(ctx, typ) if err != nil { return err } _, err = io.Copy(w, r) if err != nil { return fmt.Errorf("failed to io.Copy: %w", err) } err = w.Close() return err } // client dials the WebSocket echo server at the given url. // It then sends it 5 different messages and echo's the server's // response to each. func client(url string) error { ctx, cancel := context.WithTimeout(context.Background(), time.Minute) defer cancel() c, _, err := websocket.Dial(ctx, url, &websocket.DialOptions{ Subprotocols: []string{"echo"}, }) if err != nil { return err } defer c.Close(websocket.StatusInternalError, "the sky is falling") for i := 0; i < 5; i++ { err = wsjson.Write(ctx, c, map[string]int{ "i": i, }) if err != nil { return err } v := map[string]int{} err = wsjson.Read(ctx, c, &v) if err != nil { return err } fmt.Printf("received: %v\n", v) } c.Close(websocket.StatusNormalClosure, "") return nil }
Output: received: map[i:0] received: map[i:1] received: map[i:2] received: map[i:3] received: map[i:4]
Example (WriteOnly) ¶
This example shows how to correctly handle a WebSocket connection on which you will only write and do not expect to read data messages.
package main import ( "context" "log" "net/http" "time" "nhooyr.io/websocket" "nhooyr.io/websocket/wsjson" ) func main() { fn := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { c, err := websocket.Accept(w, r, nil) if err != nil { log.Println(err) return } defer c.Close(websocket.StatusInternalError, "the sky is falling") ctx, cancel := context.WithTimeout(r.Context(), time.Minute*10) defer cancel() ctx = c.CloseRead(ctx) t := time.NewTicker(time.Second * 30) defer t.Stop() for { select { case <-ctx.Done(): c.Close(websocket.StatusNormalClosure, "") return case <-t.C: err = wsjson.Write(ctx, c, "hi") if err != nil { log.Println(err) return } } } }) err := http.ListenAndServe("localhost:8080", fn) log.Fatal(err) }
Output:
Index ¶
- func NetConn(ctx context.Context, c *Conn, msgType MessageType) net.Conn
- type AcceptOptions
- type CloseError
- type Conn
- func (c *Conn) Close(code StatusCode, reason string) error
- func (c *Conn) CloseRead(ctx context.Context) context.Context
- func (c *Conn) Ping(ctx context.Context) error
- func (c *Conn) Read(ctx context.Context) (MessageType, []byte, error)
- func (c *Conn) Reader(ctx context.Context) (MessageType, io.Reader, error)
- func (c *Conn) SetReadLimit(n int64)
- func (c *Conn) Subprotocol() string
- func (c *Conn) Write(ctx context.Context, typ MessageType, p []byte) error
- func (c *Conn) Writer(ctx context.Context, typ MessageType) (io.WriteCloser, error)
- type DialOptions
- type MessageType
- type StatusCode
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func NetConn ¶
NetConn converts a *websocket.Conn into a net.Conn.
It's for tunneling arbitrary protocols over WebSockets. Few users of the library will need this but it's tricky to implement correctly and so provided in the library. See https://github.com/nhooyr/websocket/issues/100.
Every Write to the net.Conn will correspond to a message write of the given type on *websocket.Conn.
The passed ctx bounds the lifetime of the net.Conn. If cancelled, all reads and writes on the net.Conn will be cancelled.
If a message is read that is not of the correct type, the connection will be closed with StatusUnsupportedData and an error will be returned.
Close will close the *websocket.Conn with StatusNormalClosure.
When a deadline is hit, the connection will be closed. This is different from most net.Conn implementations where only the reading/writing goroutines are interrupted but the connection is kept alive.
The Addr methods will return a mock net.Addr that returns "websocket" for Network and "websocket/unknown-addr" for String.
A received StatusNormalClosure or StatusGoingAway close frame will be translated to io.EOF when reading.
Types ¶
type AcceptOptions ¶
type AcceptOptions struct { // Subprotocols lists the websocket subprotocols that Accept will negotiate with a client. // The empty subprotocol will always be negotiated as per RFC 6455. If you would like to // reject it, close the connection if c.Subprotocol() == "". Subprotocols []string // InsecureSkipVerify disables Accept's origin verification // behaviour. By default Accept only allows the handshake to // succeed if the javascript that is initiating the handshake // is on the same domain as the server. This is to prevent CSRF // attacks when secure data is stored in a cookie as there is no same // origin policy for WebSockets. In other words, javascript from // any domain can perform a WebSocket dial on an arbitrary server. // This dial will include cookies which means the arbitrary javascript // can perform actions as the authenticated user. // // See https://stackoverflow.com/a/37837709/4283659 // // The only time you need this is if your javascript is running on a different domain // than your WebSocket server. // Think carefully about whether you really need this option before you use it. // If you do, remember that if you store secure data in cookies, you wil need to verify the // Origin header yourself otherwise you are exposing yourself to a CSRF attack. InsecureSkipVerify bool }
AcceptOptions represents the options available to pass to Accept.
type CloseError ¶
type CloseError struct { Code StatusCode Reason string }
CloseError represents a WebSocket close frame. It is returned by Conn's methods when a WebSocket close frame is received from the peer. You will need to use the https://golang.org/pkg/errors/#As function, new in Go 1.13, to check for this error. See the CloseError example.
func (CloseError) Error ¶
func (ce CloseError) Error() string
type Conn ¶
type Conn struct {
// contains filtered or unexported fields
}
Conn represents a WebSocket connection. All methods may be called concurrently except for Reader and Read.
You must always read from the connection. Otherwise control frames will not be handled. See the docs on Reader and CloseRead.
Be sure to call Close on the connection when you are finished with it to release the associated resources.
Every error from Read or Reader will cause the connection to be closed so you do not need to write your own error message. This applies to the Read methods in the wsjson/wspb subpackages as well.
func Accept ¶
func Accept(w http.ResponseWriter, r *http.Request, opts *AcceptOptions) (*Conn, error)
Accept accepts a WebSocket handshake from a client and upgrades the the connection to a WebSocket.
Accept will reject the handshake if the Origin domain is not the same as the Host unless the InsecureSkipVerify option is set. In other words, by default it does not allow cross origin requests.
If an error occurs, Accept will always write an appropriate response so you do not have to.
Example ¶
This example accepts a WebSocket connection, reads a single JSON message from the client and then closes the connection.
package main import ( "context" "log" "net/http" "time" "nhooyr.io/websocket" "nhooyr.io/websocket/wsjson" ) func main() { fn := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { c, err := websocket.Accept(w, r, nil) if err != nil { log.Println(err) return } defer c.Close(websocket.StatusInternalError, "the sky is falling") ctx, cancel := context.WithTimeout(r.Context(), time.Second*10) defer cancel() var v interface{} err = wsjson.Read(ctx, c, &v) if err != nil { log.Println(err) return } log.Printf("received: %v", v) c.Close(websocket.StatusNormalClosure, "") }) err := http.ListenAndServe("localhost:8080", fn) log.Fatal(err) }
Output:
func Dial ¶
Dial performs a WebSocket handshake on the given url with the given options. The response is the WebSocket handshake response from the server. If an error occurs, the returned response may be non nil. However, you can only read the first 1024 bytes of its body.
You never need to close the resp.Body yourself.
This function requires at least Go 1.12 to succeed as it uses a new feature in net/http to perform WebSocket handshakes and get a writable body from the transport. See https://github.com/golang/go/issues/26937#issuecomment-415855861
Example ¶
This example dials a server, writes a single JSON message and then closes the connection.
package main import ( "context" "log" "time" "nhooyr.io/websocket" "nhooyr.io/websocket/wsjson" ) func main() { ctx, cancel := context.WithTimeout(context.Background(), time.Minute) defer cancel() c, _, err := websocket.Dial(ctx, "ws://localhost:8080", nil) if err != nil { log.Fatal(err) } defer c.Close(websocket.StatusInternalError, "the sky is falling") err = wsjson.Write(ctx, c, "hi") if err != nil { log.Fatal(err) } c.Close(websocket.StatusNormalClosure, "") }
Output:
func (*Conn) Close ¶
func (c *Conn) Close(code StatusCode, reason string) error
Close closes the WebSocket connection with the given status code and reason.
It will write a WebSocket close frame with a timeout of 5s and then wait 5s for the peer to send a close frame. Thus, it implements the full WebSocket close handshake. All data messages received from the peer during the close handshake will be discarded.
The connection can only be closed once. Additional calls to Close are no-ops.
The maximum length of reason must be 125 bytes otherwise an internal error will be sent to the peer. For this reason, you should avoid sending a dynamic reason.
Close will unblock all goroutines interacting with the connection once complete.
func (*Conn) CloseRead ¶
CloseRead will start a goroutine to read from the connection until it is closed or a data message is received. If a data message is received, the connection will be closed with StatusPolicyViolation. Since CloseRead reads from the connection, it will respond to ping, pong and close frames. After calling this method, you cannot read any data messages from the connection. The returned context will be cancelled when the connection is closed.
Use this when you do not want to read data messages from the connection anymore but will want to write messages to it.
func (*Conn) Ping ¶
Ping sends a ping to the peer and waits for a pong. Use this to measure latency or ensure the peer is responsive. Ping must be called concurrently with Reader as it does not read from the connection but instead waits for a Reader call to read the pong.
TCP Keepalives should suffice for most use cases.
func (*Conn) Read ¶
Read is a convenience method to read a single message from the connection.
See the Reader method if you want to be able to reuse buffers or want to stream a message. The docs on Reader apply to this method as well.
func (*Conn) Reader ¶
Reader waits until there is a WebSocket data message to read from the connection. It returns the type of the message and a reader to read it. The passed context will also bound the reader. Ensure you read to EOF otherwise the connection will hang.
All returned errors will cause the connection to be closed so you do not need to write your own error message. This applies to the Read methods in the wsjson/wspb subpackages as well.
You must read from the connection for control frames to be handled. Thus if you expect messages to take a long time to be responded to, you should handle such messages async to reading from the connection to ensure control frames are promptly handled.
If you do not expect any data messages from the peer, call CloseRead.
Only one Reader may be open at a time.
If you need a separate timeout on the Reader call and then the message Read, use time.AfterFunc to cancel the context passed in early. See https://github.com/nhooyr/websocket/issues/87#issue-451703332 Most users should not need this.
func (*Conn) SetReadLimit ¶
SetReadLimit sets the max number of bytes to read for a single message. It applies to the Reader and Read methods.
By default, the connection has a message read limit of 32768 bytes.
When the limit is hit, the connection will be closed with StatusMessageTooBig.
func (*Conn) Subprotocol ¶
Subprotocol returns the negotiated subprotocol. An empty string means the default protocol.
func (*Conn) Write ¶
Write is a convenience method to write a message to the connection.
See the Writer method if you want to stream a message.
func (*Conn) Writer ¶
func (c *Conn) Writer(ctx context.Context, typ MessageType) (io.WriteCloser, error)
Writer returns a writer bounded by the context that will write a WebSocket message of type dataType to the connection.
You must close the writer once you have written the entire message.
Only one writer can be open at a time, multiple calls will block until the previous writer is closed.
type DialOptions ¶
type DialOptions struct { // HTTPClient is the http client used for the handshake. // Its Transport must return writable bodies // for WebSocket handshakes. // http.Transport does this correctly beginning with Go 1.12. HTTPClient *http.Client // HTTPHeader specifies the HTTP headers included in the handshake request. HTTPHeader http.Header // Subprotocols lists the subprotocols to negotiate with the server. Subprotocols []string }
DialOptions represents the options available to pass to Dial.
type MessageType ¶
type MessageType int
MessageType represents the type of a WebSocket message. See https://tools.ietf.org/html/rfc6455#section-5.6
const ( // MessageText is for UTF-8 encoded text messages like JSON. MessageText MessageType = iota + 1 // MessageBinary is for binary messages like Protobufs. MessageBinary )
MessageType constants.
func (MessageType) String ¶
func (i MessageType) String() string
type StatusCode ¶
type StatusCode int
StatusCode represents a WebSocket status code. https://tools.ietf.org/html/rfc6455#section-7.4
const ( StatusNormalClosure StatusCode = 1000 StatusGoingAway StatusCode = 1001 StatusProtocolError StatusCode = 1002 StatusUnsupportedData StatusCode = 1003 // StatusNoStatusRcvd cannot be sent in a close message. // It is reserved for when a close message is received without // an explicit status. StatusNoStatusRcvd StatusCode = 1005 // StatusAbnormalClosure is only exported for use with Wasm. // In non Wasm Go, the returned error will indicate whether the connection was closed or not or what happened. StatusAbnormalClosure StatusCode = 1006 StatusInvalidFramePayloadData StatusCode = 1007 StatusPolicyViolation StatusCode = 1008 StatusMessageTooBig StatusCode = 1009 StatusMandatoryExtension StatusCode = 1010 StatusInternalError StatusCode = 1011 StatusServiceRestart StatusCode = 1012 StatusTryAgainLater StatusCode = 1013 StatusBadGateway StatusCode = 1014 // StatusTLSHandshake is only exported for use with Wasm. // In non Wasm Go, the returned error will indicate whether there was a TLS handshake failure. StatusTLSHandshake StatusCode = 1015 )
These codes were retrieved from: https://www.iana.org/assignments/websocket/websocket.xhtml#close-code-number
The defined constants only represent the status codes registered with IANA. The 4000-4999 range of status codes is reserved for arbitrary use by applications.
func CloseStatus ¶
func CloseStatus(err error) StatusCode
CloseStatus is a convenience wrapper around errors.As to grab the status code from a *CloseError. If the passed error is nil or not a *CloseError, the returned StatusCode will be -1.
Example ¶
This example dials a server and then expects to be disconnected with status code websocket.StatusNormalClosure.
package main import ( "context" "log" "time" "nhooyr.io/websocket" ) func main() { ctx, cancel := context.WithTimeout(context.Background(), time.Minute) defer cancel() c, _, err := websocket.Dial(ctx, "ws://localhost:8080", nil) if err != nil { log.Fatal(err) } defer c.Close(websocket.StatusInternalError, "the sky is falling") _, _, err = c.Reader(ctx) if websocket.CloseStatus(err) != websocket.StatusNormalClosure { log.Fatalf("expected to be disconnected with StatusNormalClosure but got: %+v", err) return } }
Output:
func (StatusCode) String ¶
func (i StatusCode) String() string
Source Files ¶
Directories ¶
Path | Synopsis |
---|---|
internal
|
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wsjs
Package wsjs implements typed access to the browser javascript WebSocket API.
|
Package wsjs implements typed access to the browser javascript WebSocket API. |
Package wsjson provides websocket helpers for JSON messages.
|
Package wsjson provides websocket helpers for JSON messages. |
Package wspb provides websocket helpers for protobuf messages.
|
Package wspb provides websocket helpers for protobuf messages. |