socket 'listen' error in C

Question

i'm trying to create server with TCP IP protocol

But it doesn't accept connection, or may be because of listen

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <netdb.h>
#include <strings.h>
#include <arpa/inet.h>
#include <unistd.h>

void error(char *msg)
{
perror(msg);
exit(1);
}
int main(int argc, char *argv[])
{
    int sockfd,newsockfd,num_port,serveur_T;
    socklen_t client_T;
    char buffer[200];
    struct sockaddr_in adr_serveur, adr_client;
    int n;


    if (argc < 2)
    {
        fprintf(stderr, "nombre d'arguments est insuffisant\n");
        exit(1);
    }
    sockfd=socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0)
    {
        error("erreur de creation de socket");
    }

    serveur_T=sizeof(adr_serveur);
    bzero((char*)&adr_serveur, serveur_T);
    num_port=atoi(argv[1]);

    adr_serveur.sin_family=AF_INET;
    adr_serveur.sin_addr.s_addr=INADDR_ANY;
    adr_serveur.sin_port=htons(num_port);

    serveur_T=sizeof(adr_serveur);
    if (bind ( sockfd,(struct sockaddr *) &adr_serveur,serveur_T)<0)
    {
        error(" Erreur de binding");
    }

    listen (sockfd,5);
    client_T= sizeof(adr_client);
    newsockfd= accept(sockfd,(struct sockaddr *) &adr_client,&client_T);

    if ( newsockfd<0)
    {
        error("Erreur socket accept");
    }
    bzero(buffer, 200);



return 0;}

When I execute server I got this error

Erreur socket accept: Operation not supported

Second question: Can I use an IRC client and connect it to my server ? In my school we have Linux servers so I'm wondering if I can use them as a hostname ? Thanks

Answer 1

i'm trying to create server with TCP IP protocol

You have created a SOCK_DGRAM (UDP) socket, not a SOCK_STREAM (TCP) socket. You cannot call listen() or accept() on a UDP socket, only on a TCP socket. listen() is reporting an EOPNOTSUPP error:

listen(2)

EOPNOTSUPP
The socket is not of a type that supports the listen() operation.

You are ignoring that error, and then accept() is reporting the same error:

accept(2)

EOPNOTSUPP
The referenced socket is not of type SOCK_STREAM.

There are no connections in UDP, so there is nothing to accept. Once you have bound a UDP socket to a port, you can start calling recvfrom() and sendto() on it.

In order to connect an IRC client to this server code, you need to change the socket type to SOCK_STREAM. IRC runs on TCP, not on UDP.