Send data to a tcp/port in c++ visual studio

Question

I create two applications server and client in c# and they work.I need to change the client application to c++ .Here is my code in c# :

            m_clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            IPAddress ip = IPAddress.Parse("127.0.0.1");
            int iPortNo = System.Convert.ToInt16("5000");
            IPEndPoint ipEnd = new IPEndPoint(ip, iPortNo);
            m_clientSocket.Connect(ipEnd);
            if (m_clientSocket.Connected)
            {
                    byte[] packet = CreateMessage("salam");
                    if (m_clientSocket != null)
                    {
                        m_clientSocket.Send(packet);
                    } 

            }

It works great ,so i googled c++ client code tcp and i found this URL

https://msdn.microsoft.com/en-us/library/windows/desktop/ms737591%28v=vs.85%29.aspx

Here is the above url code

#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,
        hints;
    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);
        WSACleanup();
        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,
            ptr->ai_protocol);
        if (ConnectSocket == INVALID_SOCKET) {
            printf("socket failed with error: %ld\n", WSAGetLastError());
            WSACleanup();
            return 1;
        }

        // Connect to server.
        iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
        if (iResult == SOCKET_ERROR) {
            closesocket(ConnectSocket);
            ConnectSocket = INVALID_SOCKET;
            continue;
        }
        break;
    }

    freeaddrinfo(result);

    if (ConnectSocket == INVALID_SOCKET) {
        printf("Unable to connect to server!\n");
        WSACleanup();
        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());
        closesocket(ConnectSocket);
        WSACleanup();
        return 1;
    }

    printf("Bytes Sent: %ld\n", iResult);

    // shutdown the connection since no more data will be sent
    iResult = shutdown(ConnectSocket, SD_SEND);
    if (iResult == SOCKET_ERROR) {
        printf("shutdown failed with error: %d\n", WSAGetLastError());
        closesocket(ConnectSocket);
        WSACleanup();
        return 1;
    }

    // Receive until the peer closes the connection
    do {

        iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
        if (iResult > 0)
            printf("Bytes received: %d\n", iResult);
        else if (iResult == 0)
            printf("Connection closed\n");
        else
            printf("recv failed with error: %d\n", WSAGetLastError());

    } while (iResult > 0);

    // cleanup
    closesocket(ConnectSocket);
    WSACleanup();

    return 0;
}

But the problem is i don't know which parts of this code are IP and Port?As you can see in my c# application i config the IP and port .But here in c++ code i can't find any variable to initialize the IP and Port

Answer 1

Your code appears to loop through a sequence of available ports initially set up by the line :

iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);

& then looped through here

for (ptr = result; ptr != NULL; ptr = ptr->ai_next)

with an attempt to make the connection at this line

iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);

The IP & port values are stored in the struct pointed to by the ai_addr field of the addrinfo struct. The struct pointed to by ai_addr is protocol dependant - for TCP it is a sockaddr_in struct which contains sin_port & sin_addr which is another struct of 4 bytes for the IP address. See the following links :

https://msdn.microsoft.com/en-gb/library/windows/desktop/ms737530(v=vs.85).aspx https://msdn.microsoft.com/en-gb/library/windows/desktop/ms740496(v=vs.85).aspx https://msdn.microsoft.com/en-us/library/windows/desktop/ms738571(v=vs.85).aspx