Docker 容器无法连接到我的 java 应用程序在主机上侦听，但它能够连接到其他应用程序

Question

我在 Windows 10 19042 上使用 WSL2。这是我的设置，它适用于其他应用程序，如netcat 、 npx npx http-server或python -m SimpleHTTPServer 。

在 Java 8 和 11 上测试。以下截图取自此版本。

java --version

openjdk 11.0.10 2021-01-19
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.10+9)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.10+9, mixed mode)

脚步

java ./Server.java

docker-compose up -d
ssh root@localhost -p 2222 # password is root
apt update && apt install -y netcat
nc -v docker-host 8080 # or nc -v host.docker.internal 8080

截图

• netcat 监听成功
• python -m SimpleHTTPServer 成功
• java./Server.java 失败

docker-compose.yml

version: "3.8"
services:
  docker-host:
    image: qoomon/docker-host
    cap_add: ["NET_ADMIN", "NET_RAW"]
    restart: on-failure
    environment:
      - PORTS=8080

  ssh:
    image: rastasheep/ubuntu-sshd
    ports:
      - "2222:22"

服务器.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;

public class Server implements AutoCloseable {
  private final ServerSocket server;

  public Server(String host, int port, int backlogConnectionQueueLength)
      throws UnknownHostException, IOException {
    InetAddress inetAddress = InetAddress.getByName(host);
    System.out.println("inetAddress: " + inetAddress);
    server = new ServerSocket(port, backlogConnectionQueueLength, inetAddress);
    System.out.println(Thread.currentThread() + " Created Server");
  }

  public static void main(String[] args) {
    try (Server server = new Server("localhost", 8080, 50)) {
      server.start();
    } catch (IOException e) {
      System.out.println(e);
    }
  }

  public void start() {
    System.out.println(Thread.currentThread() + " Server Ready: " + server);
    while (true) {
      acceptAndHandleClient(server);
    }
  }

  private void acceptAndHandleClient(ServerSocket server) {
    System.out.println(Thread.currentThread() + " Waiting for Incoming connections...");
    try (Socket clientSocket = server.accept()) {
      handleNewClient(clientSocket);
    } catch (IOException e) {
      e.printStackTrace();
    }
  }

  private void handleNewClient(Socket clientSocket) throws IOException {
    System.out.println(Thread.currentThread() + " Received Connection from " + clientSocket);
    BufferedReader is = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
    PrintStream os = new PrintStream(clientSocket.getOutputStream());
    // echo that data back to the client, except for QUIT.
    String line = null;
    while ((line = is.readLine()) != null) {
      System.out.println(Thread.currentThread() + " Server Got => " + line);
      if (line.equalsIgnoreCase("QUIT")) break;
      else {
        System.out.println(Thread.currentThread() + " Server echoing line back => " + line);
        os.println("Response: " + line);
        os.flush();
      }
    }
    System.out.println(Thread.currentThread() + " Server Closing Connection by Sending => Ok");
    os.println("Ok");
    os.flush();
    is.close();
    os.close();
  }

  public void close() throws IOException {
    server.close();
  }
}

Answer 1

又是作者的帖子，我意识到如何解决。 java 应用程序默认在 IPv6 上运行，它应该在 IPv4 上运行。 所以你只需要运行应用程序：

java -Djava.net.preferIPv4Stack=true ./Server.java