Android未收到来自服务器的消息

Question

我正在尝试使用Java在客户端之间进行聊天。我的服务器在python中。它运作良好。我的客户端能够将消息发送到服务器，但是他们没有从服务器接收数据。

我的客户代码是这样的：

package com.example.serverapp;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

public class MainActivity extends AppCompatActivity {

    Thread Thread1 = null;
    EditText etIP, etPort;
    TextView tvMessages;
    EditText etMessage;
    Button btnSend;
    String SERVER_IP;
    int SERVER_PORT;
    String connect = "";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        etIP = findViewById(R.id.etIP);
        etIP.setText("10.0.0.18");
        etPort = findViewById(R.id.etPort);
        etPort.setText(String.valueOf(7272));
        tvMessages = findViewById(R.id.tvMessages);
        etMessage = findViewById(R.id.etMessage);
        btnSend = findViewById(R.id.btnSend);
        Button btnConnect = findViewById(R.id.btnConnect);
        btnConnect.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                connect = etMessage.getText().toString();
                etMessage.setText("");
                Toast.makeText(MainActivity.this, connect, Toast.LENGTH_SHORT).show();
                tvMessages.setText("");
                SERVER_IP = etIP.getText().toString().trim();
                SERVER_PORT = Integer.parseInt(etPort.getText().toString().trim());
                Thread1 = new Thread(new Thread1());
                Thread1.start();
            }
        });
        btnSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String message = etMessage.getText().toString().trim();
                Toast.makeText(MainActivity.this, message, Toast.LENGTH_SHORT).show();
                if (!message.isEmpty()) {
                    new Thread(new Thread3(message)).start();
                }
            }
        });
    }

    private PrintWriter output;
    private BufferedReader input;

    class Thread1 implements Runnable {
        public void run() {
            Socket socket;
            try {
                socket = new Socket(SERVER_IP, SERVER_PORT);
                output = new PrintWriter(socket.getOutputStream());

                output.write(connect);
                output.flush();

                input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        tvMessages.setText("Connected\n");
                    }
                });
                new Thread(new Thread2()).start();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    class Thread2 implements Runnable {
        @Override
        public void run() {
            while (true) {
                try {
                    final String message = input.readLine();

                    if (message != null) {
                        runOnUiThread(new Runnable() {
                            @Override
                            public void run() {
                                tvMessages.append("server: " + message + "\n");
                            }
                        });
                    } else {
                        Thread1 = new Thread(new Thread1());
                        Thread1.start();
                        return;
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    class Thread3 implements Runnable {
        private String message;
        Thread3(String message) {
            this.message = message;
        }
        @Override
        public void run() {

            output.write(message);
            output.flush();

            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    tvMessages.append("client: " + message + "\n");
                    etMessage.setText("");
                }
            });
        }
    }
}

接收消息的线程是线程2。 我在代码中没有发现任何问题，但没有收到任何数据。