firewalld防火墙转发流量到其他端口forward port rules_firewall 端口转发

假设云主机eth0: 47.93.27.106

tun0:  inet 10.8.0.1  netmask 255.255.255.0

Show rules for a specific zone (public)

sudo firewall-cmd --zone=public --list-all

Add the tun0 interface to the public zone:

sudo firewall-cmd --zone=public --add-interface=tun0 --permanent

Check the active zones again to confirm that tun0 has been added:

sudo firewall-cmd --get-active-zones

Add the forward port rules

sudo firewall-cmd --zone=public --add-forward-port=port=14662:proto=tcp:toport=4662:toaddr=10.8.0.2 --permanent

(10.8.0.1)开放端口14662 接收外部流量, 转发到10.8.0.2:4662

修改内核参数支持IPv4防火墙端口转发

sudo sysctl -w net.ipv4.ip_forward=1
sudo sh -c 'echo "net.ipv4.ip_forward = 1" >> /etc/sysctl.conf'

 配置NAT确保public zone的流量转到en0:

sudo iptables -t nat -A PREROUTING -p tcp --dport 14662 -j DNAT --to-destination 10.8.0.2:4662
sudo iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

确保iptables-serverices软件包安装了 

sudo yum install iptables-services

保存、重启iptables，让配置生效

sudo service iptables save
sudo systemctl restart iptables
sudo systemctl enable iptables

重启防火墙firewalld

sudo firewall-cmd --reload
sudo systemctl restart firewalld

 查看改动的配置

sudo firewall-cmd --list-all --zone=public
sudo iptables -L -t nat

在这台VPS上 telnet 10.8.0.2 4662

windows客户端先连接上Open***, 另一台vps

当然也可以用在线工具open-ports, TCP可以支持, UDP还是要自己写个简单的代码测试。

windows客户端

同理udp 4672

sudo firewall-cmd --zone=public --add-forward-port=port=14672:proto=udp:toport=4672:toaddr=10.8.0.2
sudo firewall-cmd --zone=public --add-forward-port=port=14672:proto=udp:toport=4672:toaddr=10.8.0.2 --permanent
sudo firewall-cmd --reload

sudo iptables -t nat -A PREROUTING -p udp --dport 14672 -j DNAT --to-destination 10.8.0.2:4672
sudo service iptables save

sudo systemctl restart firewalld

 发送UDP报文

echo -n "Test UDP Packet" | nc -u 47.93.27.106 14672 # 以下C代码同理 

udp_sender.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>
 
int main(int argc, char *argv[]) {
    if (argc != 4) {
        fprintf(stderr, "Usage: %s <server_ip> <server_port> <message>\n", argv[0]);
        exit(EXIT_FAILURE);
    }
 
    const char *server_ip = argv[1];
    int server_port = atoi(argv[2]);
    const char *message = argv[3];
 
    int sockfd;
    struct sockaddr_in server_addr;
 
    // Create socket
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("Socket creation failed");
        exit(EXIT_FAILURE);
    }
 
    memset(&server_addr, 0, sizeof(server_addr));
 
    // Fill server information
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(server_port);
    server_addr.sin_addr.s_addr = inet_addr(server_ip);
 
    // Send UDP packet
    if (sendto(sockfd, message, strlen(message), 0, (const struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
        perror("Send failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }
 
    printf("UDP packet sent.\n");
 
    // Receive echoed packet
    char recvBuffer[512];
    struct sockaddr_in fromAddr;
    socklen_t fromAddrLen = sizeof(fromAddr);
    int bytesReceived = recvfrom(sockfd, recvBuffer, 512, 0, (struct sockaddr*)&fromAddr, &fromAddrLen);
    if (bytesReceived < 0) {
        perror("Receive failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }
 
    // Null-terminate the received data
    recvBuffer[bytesReceived] = '\0';
 
    // Print received message
    printf("Received echoed UDP packet: %s\n", recvBuffer);
 
    // Close socket
    close(sockfd);
    return 0;
}

可以把本地eMule先停掉，防止UDP 4672端口被占用

UDPEchoServer.java

package org.example;
 
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
 
public class UDPEchoServer extends JFrame {
    private JTextField portField;
    private JButton startButton;
    private JTextArea messageArea;
    private DatagramSocket socket;
    private boolean running;
 
    public UDPEchoServer() {
        setTitle("UDP Echo Server");
        setSize(400, 300);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
 
        JPanel panel = new JPanel(new BorderLayout());
        portField = new JTextField();
        startButton = new JButton("Start Server");
        messageArea = new JTextArea();
        messageArea.setEditable(false);
 
        JPanel topPanel = new JPanel(new BorderLayout());
        topPanel.add(new JLabel("Port:"), BorderLayout.WEST);
        topPanel.add(portField, BorderLayout.CENTER);
        topPanel.add(startButton, BorderLayout.EAST);
 
        panel.add(topPanel, BorderLayout.NORTH);
        panel.add(new JScrollPane(messageArea), BorderLayout.CENTER);
 
        add(panel);
 
        startButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                if (!running) {
                    int port;
                    try {
                        port = Integer.parseInt(portField.getText());
                    } catch (NumberFormatException ex) {
                        JOptionPane.showMessageDialog(UDPEchoServer.this, "Invalid port number", "Error", JOptionPane.ERROR_MESSAGE);
                        return;
                    }
                    startServer(port);
                } else {
                    stopServer();
                }
            }
        });
    }
 
    private void startServer(int port) {
        try {
            socket = new DatagramSocket(port);
            running = true;
            startButton.setText("Stop Server");
            portField.setEditable(false);
            messageArea.append("Server started on port " + port + "\n");
 
            Thread serverThread = new Thread(new Runnable() {
                @Override
                public void run() {
                    byte[] buffer = new byte[1024];
                    while (running) {
                        try {
                            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
                            socket.receive(packet);
                            String received = new String(packet.getData(), 0, packet.getLength());
                            InetAddress address = packet.getAddress();
                            int clientPort = packet.getPort();
                            messageArea.append("Received: " + received + " from " + address + ":" + clientPort + "\n");
 
                            // Echo the message back
                            DatagramPacket response = new DatagramPacket(packet.getData(), packet.getLength(), address, clientPort);
                            socket.send(response);
                            messageArea.append("Echoed: " + received + " to " + address + ":" + clientPort + "\n");
                        } catch (Exception ex) {
                            if (running) {
                                messageArea.append("Error: " + ex.getMessage() + "\n");
                            }
                        }
                    }
                }
            });
            serverThread.start();
        } catch (Exception ex) {
            messageArea.append("Error starting server: " + ex.getMessage() + "\n");
        }
    }
 
    private void stopServer() {
        running = false;
        socket.close();
        startButton.setText("Start Server");
        portField.setEditable(true);
        messageArea.append("Server stopped\n");
    }
 
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new UDPEchoServer().setVisible(true);
            }
        });
    }
}

 本地启动Java UDP Echo server测试UDP port number 4672连通性

云主机VPS发到本地Windows:

确认从云主机14672端口的UDP流量转发到windows本机的UDP 4672服务，检查UDP Echo server

确认接收到的内容与远程主机发过来的一样。

当然如果本机eMule已经启动了，端口已被占用，则需要用wireshark看

打开wireshark找到tunnel adaptor 用wireshark过滤条件 

 udp and ip.addr == 10.8.0.2 and udp.port == 4672

如果是从windows端

#include <WinSock2.h>
#include <WS2tcpip.h>
#include <stdio.h>
 
#pragma comment(lib, "Ws2_32.lib")
 
int main(int argc, char* argv[]) {
    // Validate command-line arguments
    if (argc != 4) {
        printf("Usage: %s <server_ip> <server_port> <message>\n", argv[0]);
        return 1;
    }
 
    const char* server_ip = argv[1];
    int server_port = atoi(argv[2]);
    const char* message = argv[3];
 
    // Initialize Winsock
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        printf("WSAStartup failed. Error Code : %d", WSAGetLastError());
        return 1;
    }
 
    // Create socket
    SOCKET sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sockfd == INVALID_SOCKET) {
        printf("Socket creation failed. Error Code : %d", WSAGetLastError());
        WSACleanup();
        return 1;
    }
 
    // Server address structure
    sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(server_port);
    inet_pton(AF_INET, server_ip, &serverAddr.sin_addr);
 
    // Send UDP packet
    int bytesSent = sendto(sockfd, message, strlen(message), 0, (sockaddr*)&serverAddr, sizeof(serverAddr));
    if (bytesSent == SOCKET_ERROR) {
        printf("Send failed. Error Code : %d", WSAGetLastError());
        closesocket(sockfd);
        WSACleanup();
        return 1;
    }
 
    printf("UDP packet sent.\n");
 
    // Receive echoed packet
    char recvBuffer[512];
    sockaddr_in fromAddr;
    int fromAddrLen = sizeof(fromAddr);
    int bytesReceived = recvfrom(sockfd, recvBuffer, 512, 0, (sockaddr*)&fromAddr, &fromAddrLen);
    if (bytesReceived == SOCKET_ERROR) {
        printf("Receive failed. Error Code : %d", WSAGetLastError());
        closesocket(sockfd);
        WSACleanup();
        return 1;
    }
 
    // Null-terminate the received data
    recvBuffer[bytesReceived] = '\0';
 
    // Print received message
    printf("Received echoed UDP packet: %s\n", recvBuffer);
 
    // Close socket
    closesocket(sockfd);
    WSACleanup();
    return 0;
}

udp_sender.exe 47.93.27.106 14672 "Test UDP Packet"

服务端: sudo tcpdump -i any udp port 14672 -XX

这样，借助Open***, iptables & firewalld 在没有公网IP的条件下把本机TCP 4662 映射到远程云主机 TCP 14662, 把本机UDP 4672映射到远程云主机UDP 14672。花生壳 就赚不到我们的钱了。

TCP端口连通性测试
 

windows UDP Echo server:

#include <iostream>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <windows.h>
 
#pragma comment(lib, "Ws2_32.lib")
 
#define BUFFER_SIZE 1024
 
int main() {
    WSADATA wsaData;
    SOCKET serverSocket = INVALID_SOCKET;
    sockaddr_in serverAddr, clientAddr;
    int clientAddrSize = sizeof(clientAddr);
    char buffer[BUFFER_SIZE];
 
    // Initialize Winsock
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        std::wcerr << L"WSAStartup failed with error: " << WSAGetLastError() << std::endl;
        return 1;
    }
 
    // Create a socket for the server
    serverSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (serverSocket == INVALID_SOCKET) {
        std::wcerr << L"Socket creation failed with error: " << WSAGetLastError() << std::endl;
        WSACleanup();
        return 1;
    }
 
    int port;
    std::wcout << L"Enter port number: ";
    std::wcin >> port;
 
    // Setup the UDP server address structure
    memset(&serverAddr, 0, sizeof(serverAddr));
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = INADDR_ANY;
    serverAddr.sin_port = htons(port);
 
    // Bind the socket to the port
    if (bind(serverSocket, (sockaddr*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) {
        std::wcerr << L"Bind failed with error: " << WSAGetLastError() << std::endl;
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }
 
    std::wcout << L"UDP Echo Server started on port " << port << std::endl;
 
    while (true) {
        // Receive a message from a client
        int bytesReceived = recvfrom(serverSocket, buffer, BUFFER_SIZE - 1, 0, (sockaddr*)&clientAddr, &clientAddrSize);
        if (bytesReceived == SOCKET_ERROR) {
            std::wcerr << L"recvfrom failed with error: " << WSAGetLastError() << std::endl;
            break;
        }
 
        // Null-terminate the received data
        buffer[bytesReceived] = '\0';
 
        // Echo the message back to the client
        int bytesSent = sendto(serverSocket, buffer, bytesReceived, 0, (sockaddr*)&clientAddr, clientAddrSize);
        if (bytesSent == SOCKET_ERROR) {
            std::wcerr << L"sendto failed with error: " << WSAGetLastError() << std::endl;
            break;
        }
 
        // Display received message and echo status
        WCHAR clientIp[INET_ADDRSTRLEN];
        InetNtop(AF_INET, &clientAddr.sin_addr, clientIp, INET_ADDRSTRLEN);
        std::wcout << L"Received: " << buffer << L" from " << clientIp << L":" << ntohs(clientAddr.sin_port) << std::endl;
        std::wcout << L"Echoed: " << buffer << L" to " << clientIp << L":" << ntohs(clientAddr.sin_port) << std::endl;
    }
 
    // Cleanup
    closesocket(serverSocket);
    WSACleanup();
    return 0;
}

$ ~/bin/udp_sender 云主机的公网IP 14672 "Test UDP Echo Server"
UDP packet sent.
Received echoed UDP packet: Test UDP Echo Server

如果防火墙有重复的配置，需要删除