Java客户端-服务器项目中的连接超时错误

Question

I'm learning some basic java networking stuff and I'm trying to make what I learned come to life, so when I run my server and client classes on the same computer it runs without errors, but when I take the client project to another computer and run the project after running the server it freezes and prints a connection timed out statement.

here is my server code

package sample;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextArea;
import javafx.stage.Stage;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        TextArea ta = new TextArea();
        primaryStage.setTitle("server");
        primaryStage.setScene(new Scene(new ScrollPane(ta), 450, 200));
        primaryStage.show();

        new Thread(()->{
           try {
               ServerSocket ss = new ServerSocket(8000);
               Platform.runLater(() ->
                       ta.appendText("Server started at " + new Date() + '\n'));

           Socket s = ss.accept();

           DataInputStream inputFromClient = new DataInputStream(s.getInputStream());
           DataOutputStream outputToClient = new DataOutputStream(s.getOutputStream());

           while (true) {
               double radius = inputFromClient.readDouble();

               double area = radius * radius * Math.PI;
               outputToClient.writeDouble(area);

               Platform.runLater(() -> {
                   ta.appendText("Radius received from client: "
                           + radius + '\n');
                   ta.appendText("Area is: " + area + '\n');
                   });
           }

       } catch (Exception e){
            e.printStackTrace();
       }
    }).start();
    }



public static void main(String[] args) {
    launch(args);
}
}

and this is my client

package sample;

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;

public class Main extends Application {

DataOutputStream toServer = null;
DataInputStream fromServer = null;

public void start(Stage primaryStage) {

    BorderPane pane = new BorderPane();
    pane.setPadding(new Insets(5, 5, 5, 5));
    pane.setStyle("-fx-border-color: green");
    pane.setLeft(new Label("Enter a radius: "));

    TextField tf = new TextField();
    tf.setAlignment(Pos.BOTTOM_RIGHT);
    pane.setCenter(tf);

    BorderPane mainPane = new BorderPane();

    TextArea ta = new TextArea();
    mainPane.setCenter(new ScrollPane(ta));
    mainPane.setTop(pane);
    Scene scene = new Scene(mainPane, 450, 200);
    primaryStage.setTitle("Client"); // Set the stage title
    primaryStage.setScene(scene); // Place the scene in the stage
    primaryStage.show(); // Display the stage
    tf.setOnAction(e -> {

        try {
            Socket socket = new Socket("server IP address", 8000);
            fromServer = new DataInputStream(socket.getInputStream());
            toServer = new DataOutputStream(socket.getOutputStream());
        } catch (IOException ex) {
            ta.appendText(ex.toString() + '\n');
        }

        try {
            double radius = Double.parseDouble(tf.getText().trim());

            toServer.writeDouble(radius);
            toServer.flush();

            double area = fromServer.readDouble();

            ta.appendText("Radius is " + radius + "\n");
            ta.appendText("Area received from the server is "
                    + area + '\n');
        } catch (IOException ex) {
            System.err.println(ex);
        }

    });

}
}

Answer 1

problem solved

I just had to change the network settings on my server so that it will be discoverable on my network

Answer 2

Within the server class you create a server socket on the port 8000, which is fine for both internal and external connections. However your client class attempts to create a socket with no given IP Address

Socket socket = new Socket("server IP address", 8000);

By passing the string "Server ip address", you're essentially telling java to look for a local server, as you did not pass in a proper IP Address.

So when both classes are running on the same system only the port matters, but you need to identify the IP Address of the server for the client to know where to look for its connection if they're not on the same system.