Winsock Error 10022 on Listen

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.