如何使用 Java Socket 監聽客戶端？

Question

我正在使用“ServerSocket”和“Socket”，我遇到的問題是：我使用 serverSocket 創建了一個服務器，我正在等待客戶端連接，當它連接時我會收到一些信息，這是我的問題，我如何繼續聽取客戶的意見並接受客戶的指示？

在下面的示例中，我正在創建一個服務器，當客戶端連接時，我將連接保存在“clientSocket”中。

@GET
@Path("/createServer")
public String conect() throws IOException { 
    
    serverSocket = new ServerSocket(3242);      
    clientSocket = serverSocket.accept();
    ...
    ...
  }

從這一點開始我需要一直監聽這個clientSocket，當客戶端發送一些我需要捕獲的信息來執行一些動作時，該怎么做呢？

Answer 1

ServerSocket.accept()給你一個java.net.Socket 。 文檔 在這里

從那里開始，您可以使用其輸入 stream （ Socket.getInputStream() ）讀取該套接字或寫入其 output stream （SocketOutputStream）（ Socket.getOutputStream() ）

您的 sockets（客戶端和服務器）將一直存在，直到它們close d 或垃圾收集，因此請記住，只要您需要它們，就對它們保持強烈的引用。

示例程序（簡單的回顯服務器。在客戶端中鍵入bye退出）：

服務器.java

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;
import java.util.Scanner;

public class Server {

  private static volatile boolean stopped = false;

  public static void main(String[] args) throws IOException, InterruptedException {

    try (ServerSocket server = new ServerSocket(3001)) {
      System.out.println("Server ready to accept connections on port " + server.getLocalPort());

      final Socket client = server.accept();
      System.out.println("Client connected using remote port " + client.getPort());

      final Thread t = new Thread(() -> {
        try {
          try (InputStream clientIn = client.getInputStream()) {
            try (OutputStream clientOut = client.getOutputStream()) {
              echo(clientIn, clientOut);
            }
          }
        } catch (IOException ioe) {
          ioe.printStackTrace();
          stopped = true;
        }
      });
      t.setDaemon(true);
      t.start();

      while (!stopped) {
        Thread.sleep(10);
      }
      System.out.println("Program exit");

    }

  }

  private static void echo(InputStream clientIn, OutputStream clientOut) throws IOException {
    
    try (Scanner clientScan = new Scanner(clientIn, StandardCharsets.UTF_8)) {
      try (OutputStreamWriter clientWriter = new OutputStreamWriter(clientOut, StandardCharsets.UTF_8)) {
        
        while (!stopped) {
          final String fromClient = clientScan.nextLine();
          System.out.println("In: " + fromClient);
          clientWriter.write(fromClient);
          clientWriter.write(System.lineSeparator());
          clientWriter.flush();
          if ("bye".equalsIgnoreCase(fromClient.trim())) {
            stopped = true;
          }
        }
        System.out.println("Loop done");
        
      }
    }
    
  }

}

客戶端.java

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Client {
  private static volatile boolean stopped = false;

  public static void main(String[] args) throws UnknownHostException, IOException {
    System.out.println("Client launched");
    try (Socket client = new Socket("localhost", 3001)) {
      System.out.println("Connected on remote port " + client.getPort() + " from " + client.getLocalPort());

      try (Scanner console = new Scanner(System.in)) {
        try (OutputStreamWriter toServer = new OutputStreamWriter(client.getOutputStream())) {

          final Thread t = new Thread(() -> printEverything(client));
          t.setDaemon(true);
          t.start();

          while (!stopped) {
            final String fromConsole = console.nextLine();
            if (stopped)
              break;
            toServer.write(fromConsole);
            toServer.write(System.lineSeparator());
            toServer.flush();
          }

        }
      }

    }
    System.out.println("Program exit");

  }

  private static void printEverything(Socket client) {
    try (Scanner server = new Scanner(client.getInputStream())) {
      while (!stopped) {
        final String fromServer = server.nextLine();
        System.out.println("Server said: " + fromServer);
        if ("bye".equalsIgnoreCase(fromServer.trim())) {
          stopped = true;
        }
      }
      System.out.println("Loop done. Press enter to exit");
    } catch (IOException e) {
      e.printStackTrace();
      stopped = true;
    }
  }

}