从应用程序到java服务器的Java Socket连接

Question

这个问题已经有答案了:

How can I access my localhost from my Android device? (45 个回答)

已关闭 3 年前。

我正在设置一个聊天应用程序。我有一个用java编写的带有套接字的服务器，它完美地连接到java中的示例代码。但是当我在应用程序上使用 android studio 尝试完全相同的代码时，由于某种原因它不起作用。

我尝试使用应用程序外部的代码运行它并且它有效。我已经获得了用户权限，因此它可以连接到互联网。我尝试在控制台上连接到服务器并且成功了。

客户端:

class Client implements Runnable{
    int freePort;

    @Override
    public void run() {
        connect();
    }

    private void connect(){
        System.out.println("Connecting");
        try {
            Socket socket = new Socket("localhost",1336);
            System.out.println("Connected");
            DataInputStream dataInputStream = new DataInputStream(socket.getInputStream());
            freePort = dataInputStream.readInt();
            System.out.println(freePort);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

服务器:

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;

public class DeclarationServer {
    private int numberOfClients = 0;
    DeclarationServer(){
        try {
            ServerSocket serverSocket = new ServerSocket(1336);
            while (true) {
                System.out.println(serverSocket.getLocalPort() + "__" + serverSocket.getLocalSocketAddress());
                Socket socket = serverSocket.accept();

                System.out.println(socket.getLocalSocketAddress());
                DataInputStream dataInputStream = new DataInputStream(socket.getInputStream());
                dataInputStream.readUTF();
                DataOutputStream dataOutputStream = new DataOutputStream(socket.getOutputStream());
                dataOutputStream.writeInt(1339+numberOfClients);
                dataOutputStream.flush();
                dataOutputStream.close();
                numberOfClients++;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }


    }
}

错误信息:

I/System.out: Connecting
D/ActivityThread: add activity client record, r= ActivityRecord{5f45e99 token=android.os.BinderProxy@712539a {com.example.birke.testapp/com.example.birke.testapp.MainActivity}} token= android.os.BinderProxy@712539a
D/ZrHung.AppEyeUiProbe: notify runnable to start.
W/System.err: java.net.ConnectException: failed to connect to localhost/127.0.0.1 (port 1336) from /:: (port 32940): connect failed: ECONNREFUSED (Connection refused)
        at libcore.io.IoBridge.connect(IoBridge.java:137)
        at java.net.PlainSocketImpl.socketConnect(PlainSocketImpl.java:137)
        at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:391)
        at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:231)
        at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:213)
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:436)
        at java.net.Socket.connect(Socket.java:621)
        at java.net.Socket.connect(Socket.java:570)
        at java.net.Socket.<init>(Socket.java:450)
        at java.net.Socket.<init>(Socket.java:218)
W/System.err:     at com.example.birke.testapp.Client.connect(MainActivity.java:151)
        at com.example.birke.testapp.Client.run(MainActivity.java:145)
        at java.lang.Thread.run(Thread.java:784)
    Caused by: android.system.ErrnoException: connect failed: ECONNREFUSED (Connection refused)
        at libcore.io.Linux.connect(Native Method)
        at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:118)
        at libcore.io.IoBridge.connectErrno(IoBridge.java:151)
        at libcore.io.IoBridge.connect(IoBridge.java:129)
        ... 12 more

Answer 1

看看这一行，

failed to connect to localhost/127.0.0.1 (port 1336) from /:: (port 32940): connect failed: ECONNREFUSED (Connection refused)

这意味着本地主机很可能拒绝连接，服务/服务器没有在特定端口上运行。如果服务器在同一个 Android 设备上运行，您将能够连接到本地主机。

解决方案

在初始化Socket时传递服务器的IP(如果客户端和服务器都在同一网络中，则为私有(private)IP，否则为公共(public)IP)，而不是localhost，

Socket socket = new Socket("192.168.XXX.XXX",1336);