Blocking Sockets Issue

Hey there,
I've had this problem for a little bit, and it is now time to track it down, as its become obscenely troublesome.

Premise:
I am using sockets under WinSock2 to retrieve an XML page and parse it for use.

Problem:
My socket recv() call intermittently blocks indefinately. I cannot determine a pattern to when it decides its going to block forever, but I speculate it has to do with the response time of the server? There server is a off-site box that operates with (an average) of less than 50ms ping to the development box.

Details:

Code:

	if ( WSAStartup( MAKEWORD( 2, 2 ), &wsaData ) )
		return;
	if ( ( ConnectSocket = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP ) ) == INVALID_SOCKET )
		return;
	if ( connect( ConnectSocket, (sockaddr *) &clientService, sizeof( clientService ) ) == SOCKET_ERROR )
		return;
	/* ... */
	send( ConnectSocket, outBuffer, strlen( outBuffer ), 0 );
	shutdown( ConnectSocket, 0x01 );
	do
	{
		bytes = recv( ConnectSocket, inBuffer, 1024, 0 );
		if ( bytes > 0 )
		{
			/* ... */
		}
		else if ( bytes < 0 )
		{
			Disconnect( );
			return WSAGetLastError( );
		}
		/* ... */
	} while ( bytes > 0 );
	/* ... */
	closesocket( ConnectSocket );
	WSACleanup( );

Why are you doing shutdown() immediately after send, and BEFORE doing a recv ?

How are outBuffer and inBuffer declared?

Do you attempt to add a \0 to inBuffer, even though it may be full. Doing so seems like a buffer overflow if you have char inBuffer[1024];

Originally Posted by Salem

Why are you doing shutdown() immediately after send, and BEFORE doing a recv ?

I am telling the socket that no more data is to be written to it.
shutdown Function (Windows)

Originally Posted by Salem

How are outBuffer and inBuffer declared?

One's a fixed array 1024, the other is a char* pointer of variable length depending on the length of the data I'm sending /out/.

Both operate as expected under run conditions.

Originally Posted by Salem

Do you attempt to add a \0 to inBuffer, even though it may be full. Doing so seems like a buffer overflow if you have char inBuffer[1024];

inBuffer operates as expected under run conditions.

My issue is recv() intermittantly decides to block forever, my assumption is that its based on the response time of the server, but I have no data to correlate to that (and correlation does not imply causation, anyway).

Please post back with any ideas you may have

Thanks

So you DO have a buffer of 1024.
And if you receive 1024 characters and do inBuffer[bytes] = '\0' to make it a string, you HAVE A BUFFER OVERFLOW.

Where does that \0 go? Is that the cause of your problems?

Originally Posted by Salem

So you DO have a buffer of 1024.
And if you receive 1024 characters and do inBuffer[bytes] = '\0' to make it a string, you HAVE A BUFFER OVERFLOW.

Where does that \0 go? Is that the cause of your problems?

Sorry, I should have made it clear that I am not null terminating the string; I don't think recv() would write past the 1024 limit I specified? I do not have much experience with Sockets; The rest of the language I have a fair grip on

This is not the error I'm looking for

How do you bind to the socket? I'm pretty sure that if you don't specify the socket as non-blocking then recv() is going to block when there is no data to receive. That's how it works.

All I can suggest at the moment is you run Wireshark · Go deep. to observe the connection, and try and figure out the difference between "good" and "bad" cases.

Oi. This is embarassing, the problem [seems] to be resolved. By some bizzare twist of logic the code I had written was *ahem* poorly interacting with other code I wrote, causing the socket to open and close a couple hundred times a second.

Resolved it when I was mucking about with binding (which doesn't seem to be needed if the connection being established is a client and not a server? or something?)

Anyway, thank you guys for your help, you helped me arrive at the solution

Regards,
Teeg

You need to bind to a socket if you are going to listen on it.