java - TCP 客户端/服务器通信只发送第一条消息？

Question

我正在用 java 设置一个简单的 TCP 客户端服务器交互。

服务器:

服务器是用 Java 编写的桌面客户端:

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

class TCPServer
{
    public static int PORT_NUMBER = 6129;

    public static void main(String argv[]) throws Exception
    {
        String clientMessage;
        ServerSocket welcomeSocket = new ServerSocket(PORT_NUMBER);

        while (true)
        {
            Socket connectionSocket = welcomeSocket.accept();

            BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));

            DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());

            clientMessage = inFromClient.readLine();

            System.out.println("Received: " + clientMessage);

            outToClient.writeBytes("I received this: "+ clientMessage +"\n");
        }
    }
}

---

客户:

客户端是一个通过 TCP 连接到服务器的 android 应用程序。在客户端中，我有一个方法 sendMessage(String msg) 尝试向服务器发送消息。

public static void sendMessage(String msg) throws IOException
{
    if (mainSocket == null)
    {
        return;
    }
    if (!mainSocket.isConnected())
    {
        connectSocket();
    }
    PrintWriter output = new PrintWriter( mainSocket.getOutputStream());
    output.println(msg);
    output.flush();
    System.out.println(msg);
}

问题是，服务器接收到第一条消息，但任何后续消息都不会显示。当我关闭客户端时，所有其他消息突然同时出现在服务器中。

这是服务器看到的:

Received: message 1

长时间没有 Activity ...
然后我关闭客户端

Received: message 2 message 3 message 4 message 5 etc..

我在 sendMessage() 方法中放置了一个 println，该方法本身是实时调用的。

Answer 1

每次发送消息时，您都需要在客户端显式close() 您的PrintWriter。当您完成读取 inFromClient 时，服务器端也是如此，当您完成写入 outToClient 时，同样如此。

另见 basic example , 他们很好地解释了基本的工作流程:

However, the basics are much the same as they are in this program:

Open a socket.

Open an input stream and output stream to the socket.

Read from and write to the stream according to the server's protocol.

Close the streams.

Close the socket.