//-------------------------------------------------------------------
//	sockbufs.cpp
//
//	This application demonstrates use of socket-level options to 
//	obtain the current sizes for a TCP socket's data-buffers, as
//	well as to change the current sizes of those data-buffers.
//
//	       compile using:  $ g++ sockbufs.cpp -o sockbufs
//	       execute using:  $ ./sockbufs
//
//	programmer: ALLAN CRUSE
//	written on: 26 FEB 2009
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <stdlib.h>	// for exit() 
#include <netinet/in.h>	// for socket(), getsockopt(), etc

int main( int argc, char **argv )
{
	// create a connection-oriented TCP-protocol socket 
	int	sock = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );
	if ( sock < 0 ) { perror( "socket" ); exit(1); }

	// obtain the sizes for the socket's send and receive buffers
	int		sendlen, recvlen;
	socklen_t	slen = sizeof( int );
	if ( getsockopt( sock, SOL_SOCKET, SO_SNDBUF, &sendlen, &slen ) < 0 )
		{ perror( "getsockopt SNDBUF" ); exit(1); }
	if ( getsockopt( sock, SOL_SOCKET, SO_RCVBUF, &recvlen, &slen ) < 0 )
		{ perror( "getsockopt SNDBUF" ); exit(1); }
	
	// display these initial buffer-sizes
	printf( "\n" );
	printf( " initial size of socket send-buffer: %d bytes \n", sendlen );
	printf( " initial size of socket recv-buffer: %d bytes \n", recvlen );
	printf( "\n" );

	// minimize these buffer-sizes
	sendlen = 1;
	if ( setsockopt( sock, SOL_SOCKET, SO_SNDBUF, &sendlen, slen ) < 0 )
		{ perror( "setsockopt SNDBUF" ); exit(1); }
	recvlen = 1;
	if ( setsockopt( sock, SOL_SOCKET, SO_RCVBUF, &recvlen, slen ) < 0 )
		{ perror( "setsockopt RCVBUF" ); exit(1); }
	if ( getsockopt( sock, SOL_SOCKET, SO_SNDBUF, &sendlen, &slen ) < 0 )
		{ perror( "getsockopt SNDBUF" ); exit(1); }
	if ( getsockopt( sock, SOL_SOCKET, SO_RCVBUF, &recvlen, &slen ) < 0 )
		{ perror( "getsockopt SNDBUF" ); exit(1); }
	
	// display these minimum buffer-sizes
	printf( "\n" );
	printf( " minimum size of socket send-buffer: %d bytes \n", sendlen );
	printf( " minimum size of socket recv-buffer: %d bytes \n", recvlen );
	printf( "\n" );
}