Winsock Server And Client Example: "getaddrinfo" was not declared in this scope

Question

I am trying out networking in C++ with a simple server and client, starting with some Winsock examples.

Whenever I try to compile the server with Code::Blocks, I get the following errors:

||=== Build: Debug in Server Test (compiler: GNU GCC Compiler) ===|
C:\Users\****\Desktop\Programming\CodeBlocks Projects\Server Test\main.cpp|12|warning: ignoring #pragma comment  [-Wunknown-pragmas]|
C:\Users\****\Desktop\Programming\CodeBlocks Projects\Server Test\main.cpp||In function 'int main()':|
C:\Users\****\Desktop\Programming\CodeBlocks Projects\Server Test\main.cpp|47|error: 'getaddrinfo' was not declared in this scope|
C:\Users\****\Desktop\Programming\CodeBlocks Projects\Server Test\main.cpp|57|warning: format '%ld' expects argument of type 'long int', but argument 2 has type 'int' [-Wformat]|
C:\Users\****\Desktop\Programming\CodeBlocks Projects\Server Test\main.cpp|58|error: 'freeaddrinfo' was not declared in this scope|
C:\Users\****\Desktop\Programming\CodeBlocks Projects\Server Test\main.cpp|67|error: 'freeaddrinfo' was not declared in this scope|
C:\Users\****\Desktop\Programming\CodeBlocks Projects\Server Test\main.cpp|73|error: 'freeaddrinfo' was not declared in this scope|
||=== Build failed: 4 error(s), 2 warning(s) (0 minute(s), 0 second(s)) ===|

I have tried the solution from this question, however, this results in 36 errors.

I am having the same issue with the client code.

Server Code:

#undef UNICODE

#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
#pragma comment (lib, "Ws2_32.lib")
// #pragma comment (lib, "Mswsock.lib")

#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"

int __cdecl main(void)
{
    WSADATA wsaData;
    int iResult;

    SOCKET ListenSocket = INVALID_SOCKET;
    SOCKET ClientSocket = INVALID_SOCKET;

    struct addrinfo *result = NULL;
    struct addrinfo hints;

    int iSendResult;
    char recvbuf[DEFAULT_BUFLEN];
    int recvbuflen = DEFAULT_BUFLEN;

    // 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_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_PASSIVE;

    // Resolve the server address and port
    iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
    if ( iResult != 0 ) {
        printf("getaddrinfo failed with error: %d\n", iResult);
        WSACleanup();
        return 1;
    }

    // Create a SOCKET for connecting to server
    ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
    if (ListenSocket == INVALID_SOCKET) {
        printf("socket failed with error: %ld\n", WSAGetLastError());
        freeaddrinfo(result);
        WSACleanup();
        return 1;
    }

    // Setup the TCP listening socket
    iResult = bind( ListenSocket, result->ai_addr, (int)result->ai_addrlen);
    if (iResult == SOCKET_ERROR) {
        printf("bind failed with error: %d\n", WSAGetLastError());
        freeaddrinfo(result);
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    freeaddrinfo(result);

    iResult = listen(ListenSocket, SOMAXCONN);
    if (iResult == SOCKET_ERROR) {
        printf("listen failed with error: %d\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    // Accept a client socket
    ClientSocket = accept(ListenSocket, NULL, NULL);
    if (ClientSocket == INVALID_SOCKET) {
        printf("accept failed with error: %d\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    // No longer need server socket
    closesocket(ListenSocket);

    // Receive until the peer shuts down the connection
    do {

        iResult = recv(ClientSocket, recvbuf, recvbuflen, 0);
        if (iResult > 0) {
            printf("Bytes received: %d\n", iResult);

        // Echo the buffer back to the sender
            iSendResult = send( ClientSocket, recvbuf, iResult, 0 );
            if (iSendResult == SOCKET_ERROR) {
                printf("send failed with error: %d\n", WSAGetLastError());
                closesocket(ClientSocket);
                WSACleanup();
                return 1;
            }
            printf("Bytes sent: %d\n", iSendResult);
        }
        else if (iResult == 0)
            printf("Connection closing...\n");
        else  {
            printf("recv failed with error: %d\n", WSAGetLastError());
            closesocket(ClientSocket);
            WSACleanup();
            return 1;
        }

    } while (iResult > 0);

    // shutdown the connection since we're done
    iResult = shutdown(ClientSocket, SD_SEND);
    if (iResult == SOCKET_ERROR) {
        printf("shutdown failed with error: %d\n", WSAGetLastError());
        closesocket(ClientSocket);
        WSACleanup();
        return 1;
    }

    // cleanup
    closesocket(ClientSocket);
    WSACleanup();

    return 0;
}

Answer 1

In case someone is still struggling with this issue. All you have to do is the following:

• Define _WIN32_WINNT at the beginning of your code, like this: #define _WIN32_WINNT 0x501 (used by ws2tcpip.h)
• Compile this way: g++ prog.c -o prog -lws2_32

These steps are made on both codes, server and client.

Hope this can help.

Answer 2

I don't have VS on this machine, but try importing winsock2.h before windows.h.

I do have Cygwin with gcc, and compiled the source at the command line:

gcc server.cpp -lws2_32 -oserver.exe

Seems to work:

telnet 127.0.0.1 27015

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