Java 客户端/服务器套接字

Question

我开始使用 java 套接字并且有奇怪的 [缺少] 输出。这是我的套接字方法的来源：

客户端源码：

public void loginToServer(String host, String usnm ) {
    try {
        Socket testClient = new Socket(host,1042);
        System.out.println ("Connected to host at " + host);
        logString = ("CONNECTED: " + host);
        outGoing = new PrintWriter(testClient.getOutputStream(), true);
        outGoing.print("Hello from " + testClient.getLocalSocketAddress());
        InputStream inFromServer = testClient.getInputStream();
        DataInputStream in = new DataInputStream(inFromServer);
        System.out.println("Server says " + in.readLine());
        testClient.close();
    }
    catch (Exception e) {
        System.err.println ("Error connecting to host at " + host + ":1042.\n Reason: " + e);
        logString = ("CONNECT FAILED: " + host + ":1042: " + e);
    }
    printLog(logString);
    // send server usnm and os.name [System.getProperty(os.name)] ?
}

以及服务器代码：

public void runServer() {
        try{
            server = new ServerSocket(1042); 
        }
        catch (IOException e) {
            printLog("LISTEN FAIL on 1042: " + e);
            System.err.println("Could not listen on port 1042.");
            System.exit(-1);
        }
        try{
            client = server.accept();
        }
        catch (IOException e) {
            printLog("ACCEPT FAIL on 1042: " + e);
            System.err.println("Accept failed: 1042");
            System.exit(-1);
        }
        try{
            inComing = new BufferedReader(new InputStreamReader(client.getInputStream()));
            outGoing = new PrintWriter(client.getOutputStream(), true);
        }
        catch (IOException e) {
            printLog("READ FAIL on 1042: " + e);
            System.err.println("Read failed");
            System.exit(-1);
        }
        while(true){
            try{
                clientData = inComing.readLine();
                //processingUnit(clientData, client);
                outGoing.print("Thank you for connecting to " + server.getLocalSocketAddress() + "\nGoodbye!");
            }
            catch (IOException e) {
            printLog("READ FAIL on 1042: " + e);
                System.out.println("Read failed");
                System.exit(-1);
            }
        }
    }

而客户端给出的输出仅仅是Connected to host at localhost。

发生了什么事？

Answer 1

您正在阅读线路，但您没有发送线路。将print() 更改为println()。 readLine() 将永远阻塞等待换行符。它将在流结束时返回 null，即当对等方关闭连接时，但您也没有检查它，因此您无限循环。

Answer 2

您正在编写文本并读取二进制文件。由于您的输出和输入不匹配，因此在这种情况下很可能会挂起。

我建议您使用带有 writeUTF/readUTF 的二进制文件或带有 println/readLine 的文本。

BTW：readUTF 读取两个字节以确定要读取的数据长度。由于前两个字节是 ASCII 文本，您可能要等待大约 16,000 个字符才能返回。