UNIX socket error : socket operation on non-socket - c

Question

I am trying to make a client-server communication using UNIX sockets and using the STREAM protocol.
My server is running fine, but my client is not working. Whenever I try to send or receive data, I get an error : "socket operation on non-socket". I really don't see where it comes from, because my server is very similar and I don't have any problem. My server is on my local machine (127.0.0.1) and port 5000. It is open and listening (I checked with the netstat command).
The code is there :
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <errno.h>
#define CHECK(ret, mes) if ((ret) == -1) {perror(mes); exit(-1);}
#define STRING_LENGTH 250
int createSocketINETClient(short mode, char *addr, short port)
{
int s;
struct sockaddr_in moi, server;
int moi_len, server_len;
moi.sin_family = AF_INET;
moi.sin_port = htons(port);
moi.sin_addr.s_addr = inet_addr(addr);
memset(moi.sin_zero, 0, 8);
s = socket(AF_INET, mode, 0);
CHECK(s, "socket");
moi_len = sizeof(moi);
CHECK(bind(s, (struct sockaddr*) &moi, moi_len), "bind");
return s;
}
void infoSocket (int s)
{
struct sockaddr_in sock_addr;
socklen_t len = sizeof(sock_addr);
getsockname(s, (struct sockaddr*) &sock_addr, &len);
printf("Onfo of socket %d\n", s);
printf("\t IP : %s\n", inet_ntoa(sock_addr.sin_addr));
printf("\t port : %d\n\n", ntohs(sock_addr.sin_port));
}
int main ()
{
int bytes;
int sock = createSocketINETClient(SOCK_STREAM, "0.0.0.0", 0);
struct sockaddr_in serveurSock;
int client = 0, clientSockLen = 0;
char message[] = "I am a message that is supposed to WORK !!!!\n";
char fromServer[STRING_LENGTH] = "";
infoSocket(sock);
serveurSock.sin_family = AF_INET;
serveurSock.sin_port = htons(5000);
serveurSock.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serveurSock.sin_zero, 0, 8);
CHECK(connect(sock, (struct sockaddr*) &serveurSock, sizeof(serveurSock)), "connect");
usleep(1000000);
CHECK((bytes = send(client, message, sizeof(message), 0)), "send");
printf("Message sent to server : %d bytes, \"%s\"\n", bytes, message);
CHECK((bytes = recv(client, fromServer, sizeof(fromServer), 0)), "recv");
printf("Message received from server : %d bytes, \"%s\"\n", bytes, fromServer);
close(client);
printf("Client released !\n\n");
return 0;
}
What did I do wrong ?
EDIT : The error comes from this line :
CHECK((bytes = send(client, message, sizeof(message), 0)), "send");

Answer 1

you are using the "client" variable as a socket parameter to sendto() when in fact you should use the "sock" variable.
should you strace the program, you could see the following:
connect(3, {sa_family=AF_INET, sin_port=htons(5000), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
nanosleep({tv_sec=1, tv_nsec=0}, NULL) = 0
sendto(0, "I am a message that is supposed "..., 46, 0, NULL, 0) = -1 ENOTSOCK (Socket operation on non-socket)
note the first sendto() parameter which is 0 (by default this is the stdin file descriptor) when in fact it should be 3 (see connect(...) line)
as a side note, you don't need to bind() the client socket unless you have an explicit reason to do so (using some other route than the default one, bypassing a firewall rule somewhere, etc). the os will assign by default the ip of the network interface the default route goes through and a random free port.

Answer 2

In the posted code you initialize int client = 0 and then I don't see you change it. So when you call send(0, ...) you obviously get that error.
As already mentioned by #EJP in comment to your question it can be a typo because it looks like you really was intended to use sock (as you connected it: connect(sock, ...) instead of client in call to send.