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Full Discussion: Socket programming doubt
Top Forums Programming Socket programming doubt Post 302440252 by jim mcnamara on Monday 26th of July 2010 03:17:21 PM
Old 07-26-2010
How much data of the request gets sent is under the control of the kernel. Usually for anything under ~1000 bytes you can send( ) and recv( ) everything in one go.

One way -
set socket to NON-BLOCKING, sample the input with MSG_PEEK.
Code:
int sample(int s, char *msg)
{

       int len=100;
       int nbytes=0;
       
       memset(msg, 0x0, 100);
       nbytes= recv(s, msg, len, MSG_PEEK);
       if(nbytes<0 && errno== EWOULDBLOCK)
          return EWOULDBLOCK * -1;
       else
          return nbytes;
}

This does not have error handling - note. msg now has what recv probably thinks is a message. Go back and recv() nbytes.

Good practice in something like this is to have your own protocol "header"
like
Code:
00098DT001234

00098 is length of the packet including your header
DT might mean it is data. HS might mean a heartbeat. Whatever.
The last number is a sequence that goes from 000000 -> 999999, and rolls over.
This way you can keep track of separate packets. So all you would do is sample
13 bytes, and then you know how many bytes to do a full recv() on. And you would know what to expect in the data part of the packet if any.
 

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socket.h(3)						     Library Functions Manual						       socket.h(3)

NAME
socket.h - Network addresses and sockets related classes. SYNOPSIS
#include <cc++/address.h> Classes class ost::Socket The Socket is used as the base for all Internet protocol services under Common C++. class ost::DCCPSocket DCCP sockets are used for stream based connected sessions between two sockets. class ost::UDPSocket UDP sockets implement the TCP SOCK_DGRAM UDP protocol. class ost::UDPBroadcast Representing a UDP socket used for subnet broadcasts, this class provides an alternate binding and setPeer() capability for UDP sockets. class ost::UDPTransmit Representing half of a two-way UDP connection, the UDP transmitter can broadcast data to another selected peer host or to an entire subnet. class ost::UDPReceive Representing half of a two-way UDP connection, the UDP receiver can receive data from another peer host or subnet. class ost::UDPDuplex UDP duplex connections impliment a bi-directional point-to-point UDP session between two peer hosts. class ost::TCPSocket TCP sockets are used for stream based connected sessions between two sockets. class ost::TCPV6Socket TCPV6 sockets are used for stream based connected sessions between two ipv6 sockets. class ost::TCPStream TCP streams are used to represent TCP client connections to a server by TCP protocol servers for accepting client connections. class ost::TCPSession The TCP session is used to primarily to represent a client connection that can be managed on a separate thread. class ost::SimpleTCPStream Simple TCP Stream, to be used with Common C++ Library. Namespaces namespace ost Macros #define INVALID_SOCKET -1 #define _IOLEN64 #define _IORET64 #define MSG_DONTWAIT 0 #define MSG_NOSIGNAL 0 #define SOCK_DCCP 6 #define IPPROTO_DCCP 33 #define SOL_DCCP 269 #define DCCP_SOCKOPT_AVAILABLE_CCIDS 12 #define DCCP_SOCKOPT_CCID 13 #define DCCP_SOCKOPT_TX_CCID 14 #define DCCP_SOCKOPT_RX_CCID 15 Typedefs typedef int SOCKET Variables class __EXPORT ost::SimpleTCPStream Detailed Description Network addresses and sockets related classes. Macro Definition Documentation #define _IOLEN64 Referenced by ost::SocketPort::peek(), ost::UDPSocket::peek(), ost::TCPStream::peek(), ost::SocketPort::receive(), ost::UDPReceive::receive(), ost::SocketPort::send(), ost::UDPTransmit::send(), and ost::UDPTransmit::transmit(). #define _IORET64 #define DCCP_SOCKOPT_AVAILABLE_CCIDS 12 #define DCCP_SOCKOPT_CCID 13 #define DCCP_SOCKOPT_RX_CCID 15 #define DCCP_SOCKOPT_TX_CCID 14 #define INVALID_SOCKET -1 #define IPPROTO_DCCP 33 #define MSG_DONTWAIT 0 Referenced by ost::UDPTransmit::transmit(). #define MSG_NOSIGNAL 0 Referenced by ost::UDPTransmit::send(), and ost::UDPTransmit::transmit(). #define SOCK_DCCP 6 #define SOL_DCCP 269 Typedef Documentation typedef int SOCKET Author Generated automatically by Doxygen for GNU CommonC++ from the source code. GNU CommonC++ Sat Jun 23 2012 socket.h(3)
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