无法从真正的 Android 设备访问 Node.js 的 IP 地址

Question

我使用以下代码设置了一个非常基本的 node.js 服务器：

const express = require("express");
const app = express();
const port = 8000;
const ip = '192.16x.xxx.yyy'; // the x's and y's are placeholders. I didnt want to write my real IP here
const http = require("http").createServer();

const io = require("socket.io")(http);


// using the socket, we can send/receive data to/from the client
// the server listens for the "connection" event
io.on("connection", (socket) => {

    // emit an event called "welcome" with a string as data to the client using its socket
    // so, whenever the client connects to the server, it receives this welcome message
    socket.emit("welcome", "Hello and Welcome to the Socket.io server.");

    console.log("a new client is connected.")
});

// the server listens on the specified port for incoming events
http.listen(port, ip, () => {

    console.log("Server is listening on " + ip + ":" + port);

});

因此，服务器正在侦听“连接”事件，并在客户端连接到服务器时发送欢迎消息。

Android 应用程序的客户端如下所示：

import com.github.nkzawa.socketio.client.IO;
import com.github.nkzawa.socketio.client.Socket;
import com.github.nkzawa.emitter.Emitter;


import java.net.URISyntaxException;

public class MainActivity extends AppCompatActivity {

    private Socket mSocket;
    private TextView mTextView;

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

        mTextView = findViewById(R.id.textView);

        try {
            /*
            * IO.socket() returns a socket for the specified URL and port with the
            * default options. Notice that the method caches the result, so you can
            * always get a same Socket instance for an url from any Activity or
            * Fragment.
            * */
            mSocket = IO.socket("http://192.16x.xxx.yyy:8000");

        } catch (URISyntaxException e) {
            e.getMessage();
        }

        /*
        * We then can make the socket listen an event on onCreate lifecycle callback.
        * */
        mSocket.on("welcome", onNewMessage);


        /*
        * And we explicitly call "connect()" to establish the connection here.
        * In this app, we use onCreate lifecycle callback for that, but it
        * actually depends on your application.
        * */
        mSocket.connect();
    }

    private Emitter.Listener onNewMessage = new Emitter.Listener() {
        @Override
        public void call(final Object... args) {
            MainActivity.this.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    String message = (String) args[0];
                    mTextView.setText("Received from Server: " + message);

                }
            });
        }
    };

    /*
    * Since an Android Activity has its own lifecycle, we should carefully manage the
    * state of the socket also to avoid problems like memory leaks. In this app, we’ll
    * close the socket connection and remove all listeners on onDestroy callback of
    * Activity.
    * */
    @Override
    protected void onDestroy() {

        // socket gets disconnected
        mSocket.disconnect();

        // off() removes the listener of the "welcome" event
        mSocket.off("welcome", onNewMessage);

        super.onDestroy();
    }
}

客户端代码也很简单：它连接到服务器并显示它从服务器获取的消息。 我得到了这个前任。来自官方 Socket.IO 网站https://socket.io/blog/native-socket-io-and-android/。

当我在笔记本电脑的终端上使用node server.js 启动服务器并使用 Android 模拟器时，一切正常。

但是，当我使用 USB 将真正的 Android 设备连接到笔记本电脑时，连接不会发生。

为什么 Android 应用（在真实设备中运行）无法连接到服务器？

Answer 1

这对我有用：我创建了一个 IP 为 0.0.0.0 的套接字，您应该将 node.js 上的 IP 更改为此值。

然后我打开 cmd 并输入 ipconfig 以查看我的 ip 地址是什么，这是您的本地 IP 地址。在代码中我连接到这个 IP 地址。

例如，如果您在 ipconfig 中看到 IP 192.168.178.50，则将您的 Android 代码更改为

mSocket = IO.socket("http://192.168.178.50:8000");

你的 Node.js 代码应该看起来像

const ip = '0.0.0.0';

并且不要忘记在更改 node.js 代码时重新启动服务器