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Are Qt Tcp sockets and Visual studio Sockets compatible??

  • I am trying to connect client from VS and Server from Qt , but the communication is unable to establish. But the individual Communication is working fine.

    I am working on QT c++ Project in Ubuntu . My Project needs to get the data from Sdk which runs only in Visual studio express 2012 windows. I am trying to establish communication between VS windows and QT Ubuntu via TCP/IP protocol. But it is not working.

    Are they not Compatible ?? Qt TCP Sockets and Visual Studio TCP Socket....

    Client code from Visual studio express 2012

    #define WIN32_LEAN_AND_MEAN
    #include <windows.h>
    #include <winsock2.h>
    #include <ws2tcpip.h>
    #include <stdlib.h>
    #include <stdio.h>
    // Need to link with Ws2_32.lib, Mswsock.lib, and Advapi32.lib
    #pragma comment (lib, "Ws2_32.lib")
    #pragma comment (lib, "Mswsock.lib")
    #pragma comment (lib, "AdvApi32.lib")
    #define DEFAULT_BUFLEN 512
    #define DEFAULT_PORT "27015"
    int __cdecl main(int argc, char **argv)
    WSADATA wsaData;
    SOCKET ConnectSocket = INVALID_SOCKET;
    struct addrinfo *result = NULL,
    *ptr = NULL,
    char *sendbuf = "this is a test";
    char recvbuf[DEFAULT_BUFLEN];
    int iResult;
    int recvbuflen = DEFAULT_BUFLEN;
    // Validate the parameters
    if (argc != 2) {
        printf("usage: %s server-name\n", argv[0]);
        return 1;
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed with error: %d\n", iResult);
        return 1;
    ZeroMemory( &hints, sizeof(hints) );
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    // Resolve the server address and port
    iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);
    if ( iResult != 0 ) {
        printf("getaddrinfo failed with error: %d\n", iResult);
        return 1;
    // Attempt to connect to an address until one succeeds
    for(ptr=result; ptr != NULL ;ptr=ptr->ai_next) {
        // Create a SOCKET for connecting to server
        ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype, 
        if (ConnectSocket == INVALID_SOCKET) {
            printf("socket failed with error: %ld\n", WSAGetLastError());
            return 1;
        // Connect to server.
        iResult = connect( ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
        if (iResult == SOCKET_ERROR) {
            ConnectSocket = INVALID_SOCKET;
    if (ConnectSocket == INVALID_SOCKET) {
        printf("Unable to connect to server!\n");
        return 1;
    // Send an initial buffer
    iResult = send( ConnectSocket, sendbuf, (int)strlen(sendbuf), 0 );
    if (iResult == SOCKET_ERROR) {
        printf("send failed with error: %d\n", WSAGetLastError());
        return 1;
    printf("Bytes Sent: %ld\n", iResult);
    return 0;

    Server code from QT creator 4

    #include <QtNetwork>
    #include <QObject>
    #include <QTcpServer>
    #include <QTcpSocket>
    class Server: public QObject
    Server(QObject * parent = 0);
    public slots:
    void acceptConnection();
    void startRead();
    //void Server::sendData(QTcpSocket* client, QString data);
    QTcpServer server;
    QTcpSocket* client;
    #include "server.h"
    #include <qcoreapplication.h>
    int main(int argc, char** argv)
    QCoreApplication app(argc, argv);
    Server server;
    return app.exec();
    #include "server.h"
    #include <iostream>
    using namespace std;
    Server::Server(QObject* parent): QObject(parent)
    connect(&server, SIGNAL(newConnection()),
    this, SLOT(acceptConnection()));
    server.listen(QHostAddress::Any, 27015);
    void Server::acceptConnection()
    client = server.nextPendingConnection();
    connect(client, SIGNAL(readyRead()),
    this, SLOT(startRead()));
    void Server::startRead()
    char buffer[512] = {0};
    client->read(buffer, client->bytesAvailable());
    cout << buffer << endl;

  • Qt Champions 2017

    It should work. What is the error you receive when you try to connect from the VC client to Qt Server ? Error should be able to identify the actual cause.

  • The server application running fine , but The client showing "Unable to connect to server!" , the one i have mentioned in code when it unable to find server.


  • @priya-reddy

    I guess, it is Port number issue. Check the port numbers.

    Did you check with getaddrinfo , before connect().

  • Just a wild guess, but can your firewall block the data? It just happens to me all the time...

  • @Ni.Sumi

    No, ports numbers are good. And I have disabled the firewall settings in both operating systems. The getaddrinfo is included in the client application code.
    Actually My ubuntu operating systems is in Virtual machine, not on real system. Does it effect the outside transmission??

  • @priya-reddy

    Normally,. it is allowed to communicate VM with outside OS . Also please check your VM NetWork settings.

    Is your getaddrinfo is the same , what are you looking to connect from the server application?


    I prefer to use some tool to be sure that your unbuntu is receiving the data or not. Some thing like wireshark tool / using network commands. Also few debug checks in the Qt. Try to connect and get some info like , to be sure it has no issues-

    Other than your debug message, Do you habe any error message?

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