MQL5 SocketConnect连接本地TCP服务器报4014错误，求测试示例及排查方案

背景 #

正在开发一款需连接本地TCP服务器（127.0.0.1:5001）的MQL5智能交易系统（EA）。本地服务器运行正常，可通过Telnet正常响应；已在MetaTrader的【选项→智能交易系统→允许WebRequest的网址列表】中添加127.0.0.1:5001，防火墙已禁用，端口5001处于空闲状态，但MQL5代码执行SocketConnect时始终返回错误码4014。

现有MQL5代码 #

int socket;

int OnInit()
{
    socket = SocketCreate();
    if(socket == INVALID_HANDLE)
    {
        Print("SocketCreate failed");
        return(INIT_FAILED);
    }

    if(!SocketConnect(socket, "127.0.0.1", 5001))
    {
        Print("SocketConnect failed with error: ", GetLastError());
        return(INIT_FAILED);
    }

    Print("Connected successfully");
    return(INIT_SUCCEEDED);
}

void OnDeinit(const int reason)
{
    SocketClose(socket);
}

已执行的测试 #

• 验证服务器处于监听状态且可通过Telnet访问
• 确认端口5001开放可用
• 完全禁用防火墙
• 使用数值IP 127.0.0.1而非域名
• 在MetaTrader智能交易系统选项中添加127.0.0.1:5001到允许列表
• 尝试用Netcat创建TCP服务器（nc -l 5001），但MQL5仍报4014错误

核心请求 #

需要用于MQL5测试的最简TCP服务器代码或配置示例，以明确问题出在MQL5端还是服务器端。

可用测试服务器示例 #

1. Python 最简TCP服务器 #

无需额外依赖，直接运行即可监听5001端口，收到连接后打印客户端信息并发送响应：

import socket

HOST = '127.0.0.1'
PORT = 5001

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen()
    print(f"Server listening on {HOST}:{PORT}")
    conn, addr = s.accept()
    with conn:
        print(f"Connected by {addr}")
        while True:
            data = conn.recv(1024)
            if not data:
                break
            print(f"Received: {data.decode()}")
            conn.sendall(b"Hello from test server")

运行方式：保存为test_server.py，执行python test_server.py

2. C++ 最简TCP服务器（Windows） #

基于WinSock的轻量服务器，适合Windows环境测试：

#include <winsock2.h>
#include <iostream>

#pragma comment(lib, "ws2_32.lib")

int main() {
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        std::cerr << "WSAStartup failed" << std::endl;
        return 1;
    }

    SOCKET listenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (listenSocket == INVALID_SOCKET) {
        std::cerr << "Socket creation failed: " << WSAGetLastError() << std::endl;
        WSACleanup();
        return 1;
    }

    sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serverAddr.sin_port = htons(5001);

    if (bind(listenSocket, (sockaddr*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) {
        std::cerr << "Bind failed: " << WSAGetLastError() << std::endl;
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    if (listen(listenSocket, SOMAXCONN) == SOCKET_ERROR) {
        std::cerr << "Listen failed: " << WSAGetLastError() << std::endl;
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    std::cout << "Server listening on 127.0.0.1:5001" << std::endl;

    SOCKET clientSocket = accept(listenSocket, NULL, NULL);
    if (clientSocket == INVALID_SOCKET) {
        std::cerr << "Accept failed: " << WSAGetLastError() << std::endl;
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    std::cout << "Client connected" << std::endl;

    char buffer[1024];
    int bytesReceived = recv(clientSocket, buffer, sizeof(buffer), 0);
    if (bytesReceived > 0) {
        std::cout << "Received: " << std::string(buffer, bytesReceived) << std::endl;
        const char* response = "Connected to test server";
        send(clientSocket, response, strlen(response), 0);
    }

    closesocket(clientSocket);
    closesocket(listenSocket);
    WSACleanup();
    return 0;
}

编译方式：用MinGW或MSVC编译，链接ws2_32库

验证步骤 #

1. 启动上述任一测试服务器
2. 运行MQL5 EA，查看日志是否输出Connected successfully
3. 若仍报错4014，检查MetaTrader的智能交易系统权限：确保EA被允许执行网络操作（在导航栏右键EA→属性→勾选允许自动交易和允许DLL导入/网络请求）
4. 若连接成功，说明原服务器存在兼容性问题；若仍失败，则需排查MQL5端的Socket配置或MetaTrader的网络限制

内容的提问来源于stack exchange，提问作者franzisko