Java套接字 - 读写

Question

问题:客户端没有收到任何消息.

以下是客户端和服务器的完整代码:

客户

public class Client extends Socket{


public Client(String hostName, int port) throws UnknownHostException, IOException {
    super(hostName,port);

    BufferedReader in = new BufferedReader(new InputStreamReader(getInputStream()));

    while(true) {
        String line = in.readLine();
        System.out.println("Text received: " + line);
    }

}

服务器

public final class Server extends ServerSocket{

public Server(int port) throws IOException {
    super(port);

    System.out.println("Server waiting for client 1");
    Socket client1 = accept();
    PrintWriter writer = new PrintWriter(client1.getOutputStream(), true);
    writer.write("Hello user 1");

    System.out.println("Server waiting for client 2");
    Socket client2 = accept();
    PrintWriter writer2 = new PrintWriter(client2.getOutputStream(), true);
    writer2.write("Hello user 2");

    System.out.println("Clients connected");

}

• 我启动服务器以侦听端口4444
• 我使用主机名"localhost"和端口4444启动客户端

Answer 1

您必须在邮件末尾包含换行符,如果连接未立即更改,则还要刷新PrintWriter,强制自动刷新:

writer.write("Hello user 1\n");
writer.flush();

编辑:

可以使用构造函数在PrintWriter上启用自动刷新 new PrintWriter(someOutputStream, true)

但是,如文档中所述:

如果启用了自动刷新,则只有在调用println,printf或format方法之一时才会执行,而不是每当输出换行符时

这意味着即使使用自动刷新,PrintWriter仍然必须在write调用后手动刷新,并且\n仍然必须在字符串的末尾包含换行符().

编辑2:

以下是功能齐全的客户端/服务器应用程序的一个小示例:

客户:

public static void main(String[] args){
    try{
        Socket socket = new Socket(HOST_ADDRESS, PORT);
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        System.out.println(bufferedReader.readLine());
        bufferedReader.close();
        socket.close();
    }catch(IOException e){}
}

服务器:

public static void main(String[] args){
    try{
        ServerSocket serverSocket = new ServerSocket(PORT);
        Socket socket = serverSocket.accept();
        PrintWriter printWriter = new PrintWriter(socket.getOutputStream());
        printWriter.write("Hello user!\n");
        printWriter.flush();
        printWriter.close();
        socket.close();
        serverSocket.close();
    }catch(IOException e){}
}