dgsend.c

unix linux 编程实践源代码

/*********************************************************************
 * dgsend.c  - datagram sender
 * 	         usage: dgsend hostname portnum "message"
 * 	        action: sends message to hostname:portnum
 */

#include	<stdio.h>
#include	<stdlib.h>
#include	<sys/types.h>
#include	<sys/socket.h>
#include	<netinet/in.h>

#define oops(m,x)  { perror(m);exit(x);}

int make_dgram_client_socket();
int make_internet_address(char *,int, struct sockaddr_in *);

int main(int ac, char *av[])
{
	int	sock;			/* use this socket to send	*/
	char	*msg;			/* send this messag		*/
	struct  sockaddr_in   saddr;	/* put sender's address here	*/

	if ( ac != 4 ){
		fprintf(stderr,"usage: dgsend host port 'message'\n");
		exit(1);
	}
	msg = av[3];

    /* get a datagram socket */

	if( (sock = make_dgram_client_socket()) == -1 )
		oops("cannot make socket",2);

    /* combine hostname and portnumber of destination into an address */

	if ( make_internet_address(av[1], atoi(av[2]), &saddr) == -1 )
		oops("make addr",4);

    /* send a string through the socket to that address */

	if ( sendto(sock, msg, strlen(msg), 0, 
				(struct sockaddr *)&saddr,sizeof(saddr)) == -1)
		oops("sendto failed", 3);
	return 0;
}