java - 为什么我从 WebSocket 客户端获得两个连接？一个是 "empty"

Question

当我从 Java 打开到我的 websocket 服务器应用程序的 websocket 连接时，服务器看到两个连接。第一个从不发送任何数据，第二个发送所有正确的 header ，等等。有人知道这是什么原因吗？

客户端连接是:

var websocket = new WebSocket( "ws://192.168.1.19:3333/websession" );

在服务器端，在一个 while 循环中我调用了“serverSocket.accept()”，这被调用了两次。但是其中之一从不发送任何数据(in.read() 只是最终超时而没有返回任何内容)。

JAVA 服务器代码

import java.net.*;
import java.io.*;
import java.security.*;

public class WebListener {

    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = null;
        boolean listening = true;

        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println("Could not listen on port: 4444.");
            System.exit(-1);
        }

        while (listening) new ServerThread(serverSocket.accept()).start();

        serverSocket.close();
    }
}

class ServerThread extends Thread {
    private Socket socket = null;

    public ServerThread(Socket socket) {
        super("ServerThread");
        this.socket = socket;
    }

    public void run() {

        try {
            OutputStream outStream = null;
            PrintWriter out = new PrintWriter( outStream = socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader( new InputStreamReader( socket.getInputStream()));

            String inputLine, outputLine;

            //Handle the headers first
            doHeaders( out, in );

            // ..elided..

            out.close();
            in.close();
            socket.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void doHeaders(PrintWriter out, BufferedReader in) throws Exception {
        String inputLine = null;
        String key = null;

        //Read the headers
        while ( ( inputLine = in.readLine() ) != null ) {
            //Get the key
            if ( inputLine.startsWith( "Sec-WebSocket-Key" ) ) 
                key = inputLine.substring( "Sec-WebSocket-Key: ".length() );

            //They're done
            if ( inputLine.equals( "" ) ) break;
        }

        //We need a key to continue
        if ( key == null ) throw new Exception( "No Sec-WebSocket-Key was passed!" );

        //Send our headers
        out.println( "HTTP/1.1 101 Web Socket Protocol Handshake\r" );
        out.println( "Upgrade: websocket\r" );
        out.println( "Connection: Upgrade\r" );
        out.println( "Sec-WebSocket-Accept: " + createOK( key ) + "\r" );
        out.println( "\r" );
    }

    public String createOK(String key) throws NoSuchAlgorithmException, UnsupportedEncodingException, Exception {
        String uid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
        String text = key + uid;

        MessageDigest md = MessageDigest.getInstance( "SHA-1" );
        byte[] sha1hash = new byte[40];
        md.update( text.getBytes("iso-8859-1"), 0, text.length());
        sha1hash = md.digest();

        return new String( base64( sha1hash ) );
    }

    public byte[] base64(byte[] bytes) throws Exception {
        ByteArrayOutputStream out_bytes = new ByteArrayOutputStream();
        OutputStream out = new Base64.OutputStream(out_bytes); //Using http://iharder.net/base64
        out.write(bytes);
        out.close();

        return out_bytes.toByteArray();
    }

    private String convertToHex(byte[] data) { 
        StringBuffer buf = new StringBuffer();
        for (int i = 0; i < data.length; i++) { 
            int halfbyte = (data[i] >>> 4) & 0x0F;
            int two_halfs = 0;
            do { 
                if ((0 <= halfbyte) && (halfbyte <= 9)) 
                    buf.append((char) ('0' + halfbyte));
                else 
                    buf.append((char) ('a' + (halfbyte - 10)));
                halfbyte = data[i] & 0x0F;
            } while(two_halfs++ < 1);
        } 

        return buf.toString();
    } 
}

Answer 1

这看起来是 Firefox 的一个错误。在 Chrome 中它只打开一个连接，而在 Firefox 15 中同一页面打开两个连接。