udplib.c

Unix环境下的udp编程库。

#define _UDPLIB_C

#include "udplib.h"

/*
 * Open the network connection for the server.
 *  nSockFd    :  the udp socket file identifier.
 *  sService   :  the name of the service we provide.
 *  nLocalPort :  if nonzero, this is the port to listen on
 *		          overrides the standard port for the service.
 *  noblock    :  if nonzero, not block while receiving.
 */
int openUdpConn(int *nSockFd, char *sService, int nLocalPort, int noblock)
{
	struct servent		*sp;
	struct sockaddr_in	udp_srv_addr;
	int    nRecvBuffSize;

	*nSockFd = -1;
	sp = NULL;
	if ( sService!=NULL )
	{
		/*
		 * We weren't started by a master daemon.
		 * We have to create a socket ourselves and bind our well-known
		 * address to it.
		 */
		if ( (sp = getservbyname(sService, "udp"))==NULL )
		{
			perror( "getservbyname" );
			fprintf(stderr, "openUdpConn: unknown service: %s/udp\n", sService);
		}
		if ( nLocalPort>0 && sp!=NULL )
			sp->s_port = htons(nLocalPort);	/* caller's value */
	}
	if ( ((*nSockFd)=socket(AF_INET, SOCK_DGRAM, 17))<0 )
	{
		perror( "socket" );
		fprintf( stderr, "openUdpConn: can't create datagram socket\n" );
		return -1;
	}
	/*
	 * Bind our local address so that any client can send to us.
	 */
	bzero( (char *)&udp_srv_addr, sizeof(udp_srv_addr) );
	udp_srv_addr.sin_family = AF_INET;
	udp_srv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	if ( sp!=NULL )
		udp_srv_addr.sin_port = sp->s_port;
	else if ( nLocalPort>0 )
		udp_srv_addr.sin_port = htons(nLocalPort);
	else
	{
		fprintf( stderr, "openUdpConn: no probable port\n" );
		return -1;
	}
	if ( bind(*nSockFd, (struct sockaddr *)&udp_srv_addr,
					sizeof(udp_srv_addr))<0 )
	{
		perror( "bind" );
		fprintf( stderr, "openUdpConn: can't bind local address\n" );
		return -1;
	}
	if ( noblock )
	{
		/*
		 * Set the socket to nonblocking, since program won't invoke
		 * us unless there's a datagram ready for us to read.
		 */
		noblock = 1;
		if ( ioctl( *nSockFd, FIONBIO, &noblock)<0 )
		{
			perror( "ioctl" );
			fprintf( stderr, "openUdpNet: non-block failure\n" );
			return -1;
		}
	}
    /*
     * Set receive buffer size for udp
     */
/*
    nRecvBuffSize = 512*1024;
    setsockopt(*nSockFd, SOL_SOCKET, SO_RCVBUF, &nRecvBuffSize, sizeof(nRecvBuffSize));
*/

	return 0;
}	/* end openUdpConn() */

/*
 * Receive a packet from the other end.
 * Return the length of packet,
 *  nSockFd  :  the udp socket file identifier.
 *  sBuff    :	the contents of packet that we received.
 *  nMaxLen  :	the maximum length of contents for receiving.
 *  fromaddr :	the address of the other end which sends this record.
 *  fromport :	the port of the other end which sends this record.
 */
int recvPacketFromUdp(int nSockFd, char *sBuff, int nMaxLen,
                      u_long *fromaddr, u_short *fromport)
{
	struct sockaddr_in	udp_cli_addr;
	int			addrlen, buflen;
	int			packetlen;

	addrlen = sizeof( udp_cli_addr );
	if ( (buflen=recvfrom( nSockFd, sBuff, nMaxLen, 0,
			(struct sockaddr *)&udp_cli_addr, &addrlen ))<0 )
		return (-1);
	*fromaddr = udp_cli_addr.sin_addr.s_addr;
	*fromport = udp_cli_addr.sin_port;

	sBuff[buflen] = '\0';
	sscanf( sBuff, "%4d", &packetlen );
	if ( packetlen>0 && packetlen<nMaxLen )
	{
		memcpy( sBuff, sBuff+sizeOfPckLen, packetlen );
		sBuff[packetlen] = '\0';
	} 
	else
		return (-1);

	return (packetlen);
}	/* end recvPacketFromUdp() */

/*
 * Send a record to the other end.
 * Return the length of record, -1 if failed or not sent.
 *  nSockFd  :  the udp socket file identifier.
 *  sBuff    :  the contents of record that we send.
 *  nLen     :  the length of contents.
 *  toaddr   :  the address of the other end which we send to.
 *  toport   :  the port of the other end which we send to.
 */
int sendPacketToUdp(int nSockFd, char *sBuff, int nLen,
	            u_long toaddr, u_short toport)
{
	struct sockaddr_in	udp_cli_addr;
	char			sendbuff[MaxCommBuff];
	static int		addrlen = sizeof(udp_cli_addr);

	udp_cli_addr.sin_family = AF_INET;
	udp_cli_addr.sin_addr.s_addr = toaddr;
	udp_cli_addr.sin_port = toport;

	sprintf( sendbuff, "%04d", nLen );
	if ( sBuff!=NULL && nLen>0 )
		memcpy( sendbuff+sizeOfPckLen, sBuff, nLen );
	else
		return -1;

	nLen += sizeOfPckLen;
	sendbuff[nLen] = '\0';
	if ( sendto( nSockFd, sendbuff, nLen, 0,
			(struct sockaddr *)&udp_cli_addr, addrlen )<0 )
		return (-1);

	return (nLen-sizeOfPckLen);
}	/* end sendPacketToUdp() */

/*
 * Close the connection.
 */
void closeUdpConn(int nSockFd)
{
	if ( nSockFd>=0 )
		close( nSockFd );
}	/* end closeUdpConn() */