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228 lines
9.4 KiB
Go
228 lines
9.4 KiB
Go
// Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package websocket implements the WebSocket protocol defined in RFC 6455.
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//
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// Overview
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//
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// The Conn type represents a WebSocket connection. A server application calls
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// the Upgrader.Upgrade method from an HTTP request handler to get a *Conn:
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//
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// var upgrader = websocket.Upgrader{
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// ReadBufferSize: 1024,
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// WriteBufferSize: 1024,
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// }
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//
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// func handler(w http.ResponseWriter, r *http.Request) {
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// conn, err := upgrader.Upgrade(w, r, nil)
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// if err != nil {
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// log.Println(err)
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// return
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// }
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// ... Use conn to send and receive messages.
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// }
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//
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// Call the connection's WriteMessage and ReadMessage methods to send and
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// receive messages as a slice of bytes. This snippet of code shows how to echo
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// messages using these methods:
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//
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// for {
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// messageType, p, err := conn.ReadMessage()
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// if err != nil {
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// log.Println(err)
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// return
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// }
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// if err := conn.WriteMessage(messageType, p); err != nil {
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// log.Println(err)
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// return
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// }
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// }
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//
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// In above snippet of code, p is a []byte and messageType is an int with value
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// websocket.BinaryMessage or websocket.TextMessage.
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//
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// An application can also send and receive messages using the io.WriteCloser
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// and io.Reader interfaces. To send a message, call the connection NextWriter
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// method to get an io.WriteCloser, write the message to the writer and close
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// the writer when done. To receive a message, call the connection NextReader
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// method to get an io.Reader and read until io.EOF is returned. This snippet
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// shows how to echo messages using the NextWriter and NextReader methods:
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//
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// for {
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// messageType, r, err := conn.NextReader()
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// if err != nil {
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// return
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// }
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// w, err := conn.NextWriter(messageType)
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// if err != nil {
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// return err
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// }
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// if _, err := io.Copy(w, r); err != nil {
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// return err
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// }
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// if err := w.Close(); err != nil {
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// return err
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// }
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// }
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//
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// Data Messages
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//
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// The WebSocket protocol distinguishes between text and binary data messages.
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// Text messages are interpreted as UTF-8 encoded text. The interpretation of
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// binary messages is left to the application.
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//
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// This package uses the TextMessage and BinaryMessage integer constants to
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// identify the two data message types. The ReadMessage and NextReader methods
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// return the type of the received message. The messageType argument to the
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// WriteMessage and NextWriter methods specifies the type of a sent message.
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//
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// It is the application's responsibility to ensure that text messages are
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// valid UTF-8 encoded text.
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//
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// Control Messages
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//
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// The WebSocket protocol defines three types of control messages: close, ping
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// and pong. Call the connection WriteControl, WriteMessage or NextWriter
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// methods to send a control message to the peer.
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//
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// Connections handle received close messages by calling the handler function
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// set with the SetCloseHandler method and by returning a *CloseError from the
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// NextReader, ReadMessage or the message Read method. The default close
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// handler sends a close message to the peer.
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//
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// Connections handle received ping messages by calling the handler function
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// set with the SetPingHandler method. The default ping handler sends a pong
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// message to the peer.
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//
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// Connections handle received pong messages by calling the handler function
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// set with the SetPongHandler method. The default pong handler does nothing.
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// If an application sends ping messages, then the application should set a
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// pong handler to receive the corresponding pong.
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//
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// The control message handler functions are called from the NextReader,
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// ReadMessage and message reader Read methods. The default close and ping
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// handlers can block these methods for a short time when the handler writes to
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// the connection.
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//
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// The application must read the connection to process close, ping and pong
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// messages sent from the peer. If the application is not otherwise interested
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// in messages from the peer, then the application should start a goroutine to
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// read and discard messages from the peer. A simple example is:
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//
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// func readLoop(c *websocket.Conn) {
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// for {
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// if _, _, err := c.NextReader(); err != nil {
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// c.Close()
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// break
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// }
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// }
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// }
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//
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// Concurrency
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//
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// Connections support one concurrent reader and one concurrent writer.
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//
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// Applications are responsible for ensuring that no more than one goroutine
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// calls the write methods (NextWriter, SetWriteDeadline, WriteMessage,
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// WriteJSON, EnableWriteCompression, SetCompressionLevel) concurrently and
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// that no more than one goroutine calls the read methods (NextReader,
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// SetReadDeadline, ReadMessage, ReadJSON, SetPongHandler, SetPingHandler)
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// concurrently.
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//
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// The Close and WriteControl methods can be called concurrently with all other
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// methods.
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//
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// Origin Considerations
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//
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// Web browsers allow Javascript applications to open a WebSocket connection to
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// any host. It's up to the server to enforce an origin policy using the Origin
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// request header sent by the browser.
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//
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// The Upgrader calls the function specified in the CheckOrigin field to check
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// the origin. If the CheckOrigin function returns false, then the Upgrade
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// method fails the WebSocket handshake with HTTP status 403.
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//
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// If the CheckOrigin field is nil, then the Upgrader uses a safe default: fail
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// the handshake if the Origin request header is present and the Origin host is
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// not equal to the Host request header.
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//
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// The deprecated package-level Upgrade function does not perform origin
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// checking. The application is responsible for checking the Origin header
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// before calling the Upgrade function.
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//
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// Buffers
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//
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// Connections buffer network input and output to reduce the number
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// of system calls when reading or writing messages.
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//
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// Write buffers are also used for constructing WebSocket frames. See RFC 6455,
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// Section 5 for a discussion of message framing. A WebSocket frame header is
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// written to the network each time a write buffer is flushed to the network.
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// Decreasing the size of the write buffer can increase the amount of framing
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// overhead on the connection.
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//
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// The buffer sizes in bytes are specified by the ReadBufferSize and
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// WriteBufferSize fields in the Dialer and Upgrader. The Dialer uses a default
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// size of 4096 when a buffer size field is set to zero. The Upgrader reuses
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// buffers created by the HTTP server when a buffer size field is set to zero.
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// The HTTP server buffers have a size of 4096 at the time of this writing.
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//
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// The buffer sizes do not limit the size of a message that can be read or
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// written by a connection.
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//
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// Buffers are held for the lifetime of the connection by default. If the
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// Dialer or Upgrader WriteBufferPool field is set, then a connection holds the
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// write buffer only when writing a message.
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//
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// Applications should tune the buffer sizes to balance memory use and
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// performance. Increasing the buffer size uses more memory, but can reduce the
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// number of system calls to read or write the network. In the case of writing,
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// increasing the buffer size can reduce the number of frame headers written to
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// the network.
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//
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// Some guidelines for setting buffer parameters are:
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//
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// Limit the buffer sizes to the maximum expected message size. Buffers larger
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// than the largest message do not provide any benefit.
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//
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// Depending on the distribution of message sizes, setting the buffer size to
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// a value less than the maximum expected message size can greatly reduce memory
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// use with a small impact on performance. Here's an example: If 99% of the
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// messages are smaller than 256 bytes and the maximum message size is 512
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// bytes, then a buffer size of 256 bytes will result in 1.01 more system calls
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// than a buffer size of 512 bytes. The memory savings is 50%.
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//
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// A write buffer pool is useful when the application has a modest number
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// writes over a large number of connections. when buffers are pooled, a larger
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// buffer size has a reduced impact on total memory use and has the benefit of
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// reducing system calls and frame overhead.
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//
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// Compression EXPERIMENTAL
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//
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// Per message compression extensions (RFC 7692) are experimentally supported
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// by this package in a limited capacity. Setting the EnableCompression option
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// to true in Dialer or Upgrader will attempt to negotiate per message deflate
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// support.
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//
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// var upgrader = websocket.Upgrader{
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// EnableCompression: true,
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// }
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//
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// If compression was successfully negotiated with the connection's peer, any
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// message received in compressed form will be automatically decompressed.
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// All Read methods will return uncompressed bytes.
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//
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// Per message compression of messages written to a connection can be enabled
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// or disabled by calling the corresponding Conn method:
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//
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// conn.EnableWriteCompression(false)
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//
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// Currently this package does not support compression with "context takeover".
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// This means that messages must be compressed and decompressed in isolation,
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// without retaining sliding window or dictionary state across messages. For
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// more details refer to RFC 7692.
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//
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// Use of compression is experimental and may result in decreased performance.
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package websocket
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