Winsock Error 10022 on Listen - c++

Question

i'm making a small IRC server, but I've come across a problem; upon trying to listen to the socket, i get error 10022 (Invalid Argument).
The error also appears on accept(), but this is because the socket isn't listening (the problem i'm posting about).
I didn't include the accept function because i feel it isn't necessary and would be adding pointless code.
#include <iostream>
#include <ws2tcpip.h>
#include <winsock2.h>
#include <thread>
#include <string>
#pragma comment(lib, "Ws2_32.lib")
#define maxConnections 10
class Server
{
struct sockaddr_storage their_addr;
struct addrinfo hints, *res;
struct addrinfo *servinfo;
int status;
SOCKET sock;
public:
void Start(const char *port);
};
void Server::Start(const char *port)
{
WSADATA WSAData;
if (WSAStartup(MAKEWORD(2, 0), &WSAData) != 0)
{
std::cout << "[ERROR]: " << GetLastError() << ".\n";
}
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
status = getaddrinfo(NULL, port, &hints, &res);
sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if (sock == SOCKET_ERROR)
{
std::cout << "[ERROR]: " << WSAGetLastError() << "Bad Socket.\n";
}
bind(sock, res->ai_addr, res->ai_addrlen);
Error:
if (listen(sock, maxConnections) == SOCKET_ERROR)
{
std::cout << "[ERROR]: " << WSAGetLastError() << " Listening Failed.\n";
}
The code above details the socket creation and binding, all of which are successful (though not necessarily right). The socket creation including 'NULL' might be the issue.
Thanks :)

Answer 1

WSAStartup() and getaddrinfo() do not use (WSA)GetLastError(), they directly return the actual error code instead. You are not accounting for that in your error messages.
socket() returns INVALID_SOCKET on failure, not SOCKET_ERROR.
When using getaddrinfo() to create a listening socket, you should specify AI_PASSIVE in the addrinfo.ai_flags field of the hints parameter. That will fill the output addrinfo with data that is suitable to pass to bind().
Try something more like this:
class Server
{
private:
bool winsockStarted;
SOCKET sock;
...
public:
Server();
~Server();
bool Start(const char *port);
void Stop();
...
};
Server::Server()
: sock(INVALID_SOCKET), winsockStarted(false)
{
WSADATA WSAData = {0};
int status = WSAStartup(MAKEWORD(2, 0), &WSAData);
if (status != 0)
std::cout << "[ERROR]: " << status << " Unable to start Winsock." << std::endl;
else
winsockStarted = true;
}
Server::~Server()
{
Stop();
if (winsockStarted)
WSACleanup();
}
bool Server::Start(const char *port)
{
Stop();
struct addrinfo hints = {0};
struct addrinfo *res = NULL;
hints.ai_flags = AI_PASSIVE;
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
int status = getaddrinfo(NULL, port, &hints, &res);
if (status != 0)
{
std::cout << "[ERROR]: " << status << " Unable to get address info for Port " << port << "." << std::endl;
return false;
}
SOCKET newsock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if (newsock == INVALID_SOCKET)
{
std::cout << "[ERROR]: " << WSAGetLastError() << " Unable to create Socket." << std::endl;
freeaddrinfo(res);
return false;
}
if (bind(newsock, res->ai_addr, res->ai_addrlen) == SOCKET_ERROR)
{
std::cout << "[ERROR]: " << WSAGetLastError() << " Unable to bind Socket." << std::endl;
freeaddrinfo(res);
closesocket(newsock);
return false;
}
freeaddrinfo(res);
if (listen(newsock, maxConnections) == SOCKET_ERROR)
{
std::cout << "[ERROR]: " << WSAGetLastError() << " Unable to Listen on Port " << port << "." << std::endl;
closesocket(newsock);
return false;
}
sock = newsock;
return true;
}
void Server::Stop()
{
if (sock != INVALID_SOCKET)
{
closesocket(sock);
sock = INVALID_SOCKET;
}
}

Answer 2

I reread my code and realized that i need to add a check here
status = getaddrinfo(NULL, port, &hints, &res);
I changed it to
if (status = getaddrinfo(NULL, port, &hints, &res) != 0)
{
std::cout << "[ERROR]: " << WSAGetLastError() << "Get Address Info failed.\n";
}
and startup was successful.
If someone could explain why, i'll improve my answer.