Windows Socket Encapsulation - Unresolved external symbol

Question

I'm learning winsockets and got a linker error when calling the socket(af, type, protocol) function in a constructor.

main.cpp

#include "Server.h"

int main(int argc, char **argv) {
    nmd::Server *server = new nmd::Server();

    //TODO: Logic

    delete server;
    server = nullptr;
    return 0;
}

Server.h

#pragma once

#include <WinSock2.h>
#include <WS2tcpip.h>

namespace nmd {
class Server {
public:
    Server();
    virtual ~Server();
private:
    SOCKET socket_;
};
}

Server.cpp

#include "Server.h"

nmd::Server::Server() {
    socket_ = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (INVALID_SOCKET == socket_)
        throw 1; // TODO: proper exception handling
}

nmd::Server::~Server() {}

When I try to build it, an unresolved external symbol error occur. In detail:

LNK2019 unresolved external symbol __imp__socket@12 referenced in function "public: __thiscall nmd::Server::Server(void)" (??0Server@nmd@@QAE@XZ)

What am I missing here? I want to know the source of this problem, not only the solution. What makes the compiler to belive that nmd::Server::Server() is undefined when I put the socket(...) function in it?

Answer 1

You need to add Ws2_32.lib to your linker command to resolve that function.