[C] [Network] [UDP] recvfrom() failed while Binding localhost

Hi there,

I might need a little help from some C expert in network programming !

I am binding a UDP socket to localhost ("127.0.0.1"), this is recieving all the messages sent as it should, but my problem is that if I press ENTER, it makes the socket failed :

recvfrom() failed: Socket operation on non-socket

I have other sockets bind to multicast addresses which work fine, and if I comment out the Unicast socket, I can press ENTER when the program is running.

Here is how I am binding my socket :

Code:

int UDPSock(const char* ip_addr,const char* port)
{
	int sockfd;
	struct sockaddr_storage Addr;
	memset(&Addr, 0, sizeof(Addr));
	if (get_addr(ip_addr, port, PF_UNSPEC,SOCK_DGRAM, &Addr) <0)
	{
		fprintf(stderr, "get_addr error:: could not find multicast address=[%s] port=[%s]\n", multicast_ip, port);
		return -1;
	}
	
	//Create and bind the socket
	sockfd = socket(Addr.ss_family, SOCK_DGRAM, 0);
	if (bind(sockfd, (struct sockaddr *)&Addr, sizeof(Addr)) < 0)
	{
		perror("bind error:: ");
		close(sockfd);
		return -1;
	}
	return sockfd;
}

Code:

int main()
{
int number_of_sockets=4;
char sockets[4];	
	sockets[0]=UDPMulicastSock(ipv4,port);
	sockets[1]=UDPMulicastSock(ipv4_2,port);
	sockets[2]=UDPMulicastSock(ipv4_3,port);
	sockets[3]=UDPMulicastSock(ipv6,port);
        sockets[4]=UDPSock(Unicast,port);
	while(1)
	{
		int largest = 0;
		FD_ZERO(&readReadySet);
		for (i = 0; i < number_of_sockets; ++i)
		{
		  FD_SET(sockets[i], &readReadySet);
		  if (largest < sockets[i])
		  {
		    largest = sockets[i];
		  }
		}
		rc = select(largest + 1, &readReadySet, NULL, NULL, NULL);
		if (rc == -1)
		{
		  /* select( ) error */
		}
		else if (rc == 0)
		{
		  /* No sockets ready */
		}
		else
		{
			for (i = 0; i < number_of_sockets; ++i)
			{
				if (FD_ISSET(sockets[i], &readReadySet))
				{
					/* Clear the receive buffers & structs */
					memset(recv_str, 0, sizeof(recv_str));
					from_len = sizeof(from_addr);
					memset(&from_addr, 0, from_len);
					/* Block waiting to receive a packet */
					recv_len = recvfrom(sockets[i], recv_str, MAX_LEN, 0,(struct sockaddr*)&from_addr, &from_len);
					if(recv_len<0)
					{
						printf("\nrecv_len==%i",recv_len);
						perror("recvfrom() failed");
						exit(1);
					...}

I might have a bug somewhere which I do not find, or some behaviour of socket that I do not know/understand because I was not suspecting that pressing ENTER would be seen as a socket entry.

Thanks by advance for your help, or even to have read me.

Regards,
Sismon

> number_of_sockets
Do we assume this contains 5 ?

> sockets[4]
Do we assume this is an array with at least 5 elements?

Do we assume your UDPSock() didn't print an error message, and didn't return -1?

Hi Salem,

Oh yes, sorry if I miss some details, but as my program begins to have numbers of line I did not want to flood the post...

So to give more details :


>> number_of_sockets
>Do we assume this contains 5 ?

Code:

int number_of_sockets=4;

>> sockets[4]
>Do we assume this is an array with at least 5 elements?

Code:

char sockets[4];

And for the last one I am not sure of what you mean ?!? As it would return -1 if cannot "getaddr" or cannot "bind".

But I have no such error at the moment.

Please let me know if you would need more details, as I am not really sure what would help you ?

Thanks for your comment.

NB: I edit my first post

Code:

sockets[4]=UDPSock(Unicast,port);

There is no member with index 4 in your array

UDPSock returns int - char is too small to store this value

Oh yes !!

Such bad mistakes, and I did not even noticed it....

What surprise me is that the compiler was not complaining at all...

One socket assigned out of the range

And a socket file descriptor as a char....

Thank you very much to both of you !

Now many other happy error to correct, but that's my part....MALLOC error and so on...

Thanks !

Sismon