Thread: non-blocking socket with a timeout

Hi everyone...
I was trying to read other threads before I submit a duplicate, but I think I have some conceptual problem about setting non-blocking sockets with timeouts.

Basically, what I want to do is setup a socket that if the send/receive wait for 10 seconds, they will move on (do other important stuff).

That said, I realized that I need a non-blocking socket. This is the code (in snippets) that I have so far but I am not seeing what I think I should.

Code:

   	/* set timeouts for send/receive on this socket */
	tv.tv_sec = 10; /* seconds */
	tv.tv_usec = 0;
	opt = 1;

	/* Hard coded for now */
	port_num = 5432;

	/* Create our socket */
	main_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

	/* Set it up with an address */
	memset(&sock_info, 0, sizeof(struct sockaddr_in));
	sock_info.sin_family = AF_INET;
	sock_info.sin_port = htons((unsigned short)port_num);
	sock_info.sin_addr.s_addr = htonl(INADDR_ANY);
	status = bind(main_socket, &sock_info, sizeof(struct sockaddr_in));
	/* listen for connection requests */
	status = listen(main_socket, 1); /* set to only one connection */

		/* Wait until we get one */
		accept_socket = -1;
		accept_socket = accept(main_socket, &client_info, &info_len);
		if (accept_socket > 0)
		{
			ioctl(accept_socket, FIONBIO, &opt);

			
			if(setsockopt(accept_socket, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv)) < 0)
			{
				printf("Cannot Set SO_SNDTIMEO for socket\n");
			}
			
			if(setsockopt(accept_socket, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0)
			{
				printf("Cannot Set SO_RCVTIMEO for socket\n");
			}
		}

After this point, I expect the socket to wait until it receives a packet for 10 seconds before it barfs...

Code:

        rcv_len = recv(accept_socket, my_message, MSG_SIZE, 0);
	if( rcv_len < 0)
	{
		printf("Nothing received");
	}
	else if(rcv_len >= 0)
	{
		printf("Received something2...");
	}
        ...
        ...
        ...
        ...

but it takes less than a second to quit on me...

By the way, I know that some might recommend
fcntl( accept_socket, O_NONBLOCK, 0 );
over what I have, but I am required to use the method I included in the code.

Can anyone shed some light on my senario?

thanks in advance.

Thanks Salem for your reply.
I did leave out a bit of code that does error handling and checking.

Before I clarify what I meant with "takes less than a second to quit on me" let me say this first.

In a blocking socket, a recv() function call will hold until something is received, hence the blocking part of the socket. However, when I set the socket to non-blocking, my understanding is that a recv() call will wait x seconds (based on what I set the SO_RCVTIMEO value to) and then it exists with an error -1 and errno set properly. However, this is not happening.

As I mentioned in my first (original) post, is I could easily have some conceptual misunderstanding.

How do I use the select() function? I guess I could also read up on it but if you don't mind dropping a few lines that would be greatly appreciated.

Thanks brewbuck.
So now I have re-written some of the code to utilize the select() function among others FD_SET, FD_ISSET, etc...
I am still seeing some weird behavior, but I will work on it some more and see if I still need to post a question about it....

Thanks for the reply again.

I need to ask a really dumb question....
If I create a non-blocking socket, it needs to be implemented on the host and the client, correct?

thanks

Salem,
Thanks again for your input. I guess I wasn't thinking too much about it or else the scenario you mentioned would clearly provide an answer.

My question now is after looking at this for some time, I am starting to get the hang of it, but i wanted to know if I can do something like the following code. What I want to do is I want to use the select for send() and recv() functions to synch. I might still be using the code incorrectly, but I thought I would dump it here and get someone more knowledgeable to look at it.

Code:

...
...
...

FD_ZERO(&read_mask);
FD_ZERO(&write_mask);

FD_SET(accept_socket, &read_mask);
FD_SET(accept_socket, &write_mask);

/* handle receiving the packet */
select_return = select(accept_socket, &read_mask, (fd_set *)0, (fd_set *)0, &tv);
if(select_return < 0) /* [timeout=0, -1= ERROR] is returned */
{
	printf("recv: select functions returned -1 error value\n");
}
else if(select_return == 0)
{
	printf("recv: select functions returned 0 timeout value\n");
}
else
{
	printf("recv: select functions returned a positive value\n");
	
	if(FD_ISSET(accept_socket, &read_mask))
	{
		/*  HAND SHAKE AS A START */
		rcv_len = recv(accept_socket, myDmsg, MSG_SIZE, 0);
				
		if( rcv_len < 0)
		{
			strcpy(myDmsg, "Nothing received");
			isConnected = FALSE;
		}
		else if(rcv_len >= 0)
		{
			strcpy(myDmsg, "Received something2...");
		}
	}
}

/* handle sending the packet */
select_return = select(accept_socket, (fd_set *)0, &write_mask, (fd_set *)0, &tv);

if(select_return < 0) /* [timeout=0, -1= ERROR] is returned */
{
	printf("send: select functions returned -1 error value\n");
}
else if(select_return == 0)
{
	printf("send: select functions returned 0 timeout value\n");
}
else
{
	printf("send: select functions returned a positive value\n");
			
	if( send(accept_socket, myDmsg, strlen(myDmsg), 0) < 0)
	{
		/* an error occurred. Handle it appropriately (TODO) */
	}
}
...
...
...

Adding some comments.
The previous code seems to actually work (post #8) with the one minor change of all select functions need to be as follows:

Code:

select_return = select(accept_socket+1, ..... );

That did the trick.....
thanks everyone who provided some comments and thoughts regarding this question.