Source file src/pkg/websocket/server.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package websocket
     6	
     7	import (
     8		"http"
     9		"io"
    10		"strings"
    11	)
    12	
    13	/*
    14	Handler is an interface to a WebSocket.
    15	
    16	A trivial example server:
    17	
    18		package main
    19	
    20		import (
    21			"http"
    22			"io"
    23			"websocket"
    24		)
    25	
    26		// Echo the data received on the Web Socket.
    27		func EchoServer(ws *websocket.Conn) {
    28			io.Copy(ws, ws);
    29		}
    30	
    31		func main() {
    32			http.Handle("/echo", websocket.Handler(EchoServer));
    33			err := http.ListenAndServe(":12345", nil);
    34			if err != nil {
    35				panic("ListenAndServe: " + err.String())
    36			}
    37		}
    38	*/
    39	type Handler func(*Conn)
    40	
    41	/*
    42	Gets key number from Sec-WebSocket-Key<n>: field as described
    43	in 5.2 Sending the server's opening handshake, 4.
    44	*/
    45	func getKeyNumber(s string) (r uint32) {
    46		// 4. Let /key-number_n/ be the digits (characters in the range
    47		// U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9)) in /key_1/,
    48		// interpreted as a base ten integer, ignoring all other characters
    49		// in /key_n/.
    50		r = 0
    51		for i := 0; i < len(s); i++ {
    52			if s[i] >= '0' && s[i] <= '9' {
    53				r = r*10 + uint32(s[i]) - '0'
    54			}
    55		}
    56		return
    57	}
    58	
    59	// ServeHTTP implements the http.Handler interface for a Web Socket
    60	func (f Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
    61		rwc, buf, err := w.(http.Hijacker).Hijack()
    62		if err != nil {
    63			panic("Hijack failed: " + err.String())
    64			return
    65		}
    66		// The server should abort the WebSocket connection if it finds
    67		// the client did not send a handshake that matches with protocol
    68		// specification.
    69		defer rwc.Close()
    70	
    71		if req.Method != "GET" {
    72			return
    73		}
    74		// HTTP version can be safely ignored.
    75	
    76		if strings.ToLower(req.Header.Get("Upgrade")) != "websocket" ||
    77			strings.ToLower(req.Header.Get("Connection")) != "upgrade" {
    78			return
    79		}
    80	
    81		// TODO(ukai): check Host
    82		origin := req.Header.Get("Origin")
    83		if origin == "" {
    84			return
    85		}
    86	
    87		key1 := req.Header.Get("Sec-Websocket-Key1")
    88		if key1 == "" {
    89			return
    90		}
    91		key2 := req.Header.Get("Sec-Websocket-Key2")
    92		if key2 == "" {
    93			return
    94		}
    95		key3 := make([]byte, 8)
    96		if _, err := io.ReadFull(buf, key3); err != nil {
    97			return
    98		}
    99	
   100		var location string
   101		if req.TLS != nil {
   102			location = "wss://" + req.Host + req.URL.RawPath
   103		} else {
   104			location = "ws://" + req.Host + req.URL.RawPath
   105		}
   106	
   107		// Step 4. get key number in Sec-WebSocket-Key<n> fields.
   108		keyNumber1 := getKeyNumber(key1)
   109		keyNumber2 := getKeyNumber(key2)
   110	
   111		// Step 5. get number of spaces in Sec-WebSocket-Key<n> fields.
   112		space1 := uint32(strings.Count(key1, " "))
   113		space2 := uint32(strings.Count(key2, " "))
   114		if space1 == 0 || space2 == 0 {
   115			return
   116		}
   117	
   118		// Step 6. key number must be an integral multiple of spaces.
   119		if keyNumber1%space1 != 0 || keyNumber2%space2 != 0 {
   120			return
   121		}
   122	
   123		// Step 7. let part be key number divided by spaces.
   124		part1 := keyNumber1 / space1
   125		part2 := keyNumber2 / space2
   126	
   127		// Step 8. let challenge be concatenation of part1, part2 and key3.
   128		// Step 9. get MD5 fingerprint of challenge.
   129		response, err := getChallengeResponse(part1, part2, key3)
   130		if err != nil {
   131			return
   132		}
   133	
   134		// Step 10. send response status line.
   135		buf.WriteString("HTTP/1.1 101 WebSocket Protocol Handshake\r\n")
   136		// Step 11. send response headers.
   137		buf.WriteString("Upgrade: WebSocket\r\n")
   138		buf.WriteString("Connection: Upgrade\r\n")
   139		buf.WriteString("Sec-WebSocket-Location: " + location + "\r\n")
   140		buf.WriteString("Sec-WebSocket-Origin: " + origin + "\r\n")
   141		protocol := strings.TrimSpace(req.Header.Get("Sec-Websocket-Protocol"))
   142		if protocol != "" {
   143			buf.WriteString("Sec-WebSocket-Protocol: " + protocol + "\r\n")
   144		}
   145		// Step 12. send CRLF.
   146		buf.WriteString("\r\n")
   147		// Step 13. send response data.
   148		buf.Write(response)
   149		if err := buf.Flush(); err != nil {
   150			return
   151		}
   152		ws := newConn(origin, location, protocol, buf, rwc)
   153		ws.Request = req
   154		f(ws)
   155	}
   156	
   157	/*
   158	Draft75Handler is an interface to a WebSocket based on the
   159	(soon obsolete) draft-hixie-thewebsocketprotocol-75.
   160	*/
   161	type Draft75Handler func(*Conn)
   162	
   163	// ServeHTTP implements the http.Handler interface for a Web Socket.
   164	func (f Draft75Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
   165		if req.Method != "GET" || req.Proto != "HTTP/1.1" {
   166			w.WriteHeader(http.StatusBadRequest)
   167			io.WriteString(w, "Unexpected request")
   168			return
   169		}
   170		if req.Header.Get("Upgrade") != "WebSocket" {
   171			w.WriteHeader(http.StatusBadRequest)
   172			io.WriteString(w, "missing Upgrade: WebSocket header")
   173			return
   174		}
   175		if req.Header.Get("Connection") != "Upgrade" {
   176			w.WriteHeader(http.StatusBadRequest)
   177			io.WriteString(w, "missing Connection: Upgrade header")
   178			return
   179		}
   180		origin := strings.TrimSpace(req.Header.Get("Origin"))
   181		if origin == "" {
   182			w.WriteHeader(http.StatusBadRequest)
   183			io.WriteString(w, "missing Origin header")
   184			return
   185		}
   186	
   187		rwc, buf, err := w.(http.Hijacker).Hijack()
   188		if err != nil {
   189			panic("Hijack failed: " + err.String())
   190			return
   191		}
   192		defer rwc.Close()
   193	
   194		var location string
   195		if req.TLS != nil {
   196			location = "wss://" + req.Host + req.URL.RawPath
   197		} else {
   198			location = "ws://" + req.Host + req.URL.RawPath
   199		}
   200	
   201		// TODO(ukai): verify origin,location,protocol.
   202	
   203		buf.WriteString("HTTP/1.1 101 Web Socket Protocol Handshake\r\n")
   204		buf.WriteString("Upgrade: WebSocket\r\n")
   205		buf.WriteString("Connection: Upgrade\r\n")
   206		buf.WriteString("WebSocket-Origin: " + origin + "\r\n")
   207		buf.WriteString("WebSocket-Location: " + location + "\r\n")
   208		protocol := strings.TrimSpace(req.Header.Get("Websocket-Protocol"))
   209		// canonical header key of WebSocket-Protocol.
   210		if protocol != "" {
   211			buf.WriteString("WebSocket-Protocol: " + protocol + "\r\n")
   212		}
   213		buf.WriteString("\r\n")
   214		if err := buf.Flush(); err != nil {
   215			return
   216		}
   217		ws := newConn(origin, location, protocol, buf, rwc)
   218		f(ws)
   219	}
The Go Programming Language

Source file src/pkg/websocket/server.go
