Add WebSocket server framework hooked into http.

R=r, rsc
https://golang.org/cl/156071

src/pkg/websocket/server.go

@@ -0,0 +1,73 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package websocket
+
+import (
+	"http";
+	"io";
+)
+
+// Handler is a interface that use a WebSocket.
+//
+// A trivial example server is:
+//
+//  package main
+//
+//  import (
+//     "http"
+//     "io"
+//     "websocket"
+//  )
+//
+//  // echo back the websocket.
+//  func EchoServer(ws *websocket.Conn) {
+//       io.Copy(ws, ws);
+//  }
+//
+//  func main() {
+//    http.Handle("/echo", websocket.Handler(EchoServer));
+//    err := http.ListenAndServe(":12345", nil);
+//    if err != nil {
+//        panic("ListenAndServe: ", err.String())
+//    }
+//  }
+type Handler func(*Conn)
+
+func (f Handler) ServeHTTP(c *http.Conn, req *http.Request) {
+	if req.Method != "GET" || req.Proto != "HTTP/1.1" ||
+		req.Header["Upgrade"] != "WebSocket" ||
+		req.Header["Connection"] != "Upgrade" {
+		c.WriteHeader(http.StatusNotFound);
+		io.WriteString(c, "must use websocket to connect here");
+		return;
+	}
+	rwc, buf, err := c.Hijack();
+	if err != nil {
+		panic("Hijack failed: ", err.String());
+		return;
+	}
+	defer rwc.Close();
+	origin := req.Header["Origin"];
+	location := "ws://" + req.Host + req.URL.Path;
+
+	// TODO(ukai): verify origin,location,protocol.
+
+	buf.WriteString("HTTP/1.1 101 Web Socket Protocol Handshake\r\n");
+	buf.WriteString("Upgrade: WebSocket\r\n");
+	buf.WriteString("Connection: Upgrade\r\n");
+	buf.WriteString("WebSocket-Origin: " + origin + "\r\n");
+	buf.WriteString("WebSocket-Location: " + location + "\r\n");
+	protocol := "";
+	// canonical header key of WebSocket-Protocol.
+	if protocol, found := req.Header["Websocket-Protocol"]; found {
+		buf.WriteString("WebSocket-Protocol: " + protocol + "\r\n")
+	}
+	buf.WriteString("\r\n");
+	if err := buf.Flush(); err != nil {
+		return
+	}
+	ws := newConn(origin, location, protocol, buf, rwc);
+	f(ws);
+}