Socket datagram

[hubert at spica.ucsb.edu]

Hi! I am testing the socket's datagram facility and I can't figure
out why the following program doesn't work. The a.out give me
error message like "bad address". Could someone explain it ?

By the way,  I just want to use these system call instead of 
the listen ,accept and connect  for the socket_stream.

Thanks.



#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>


main()
{
int s1,s2,ret;
char mesg0[20],mesg1[20],mesg2[20],mesg3[20],mesg4[20];
struct sockaddr	sock1,sock2;

	sock1.sa_family=PF_UNIX;
	sock2.sa_family=PF_UNIX;

	sprintf(sock1.sa_data,"sock1");
	sprintf(sock2.sa_data,"sock2");

	unlink(sock1.sa_data);
	unlink(sock2.sa_data);

	if ((s2=socket(PF_UNIX, SOCK_DGRAM,0)) == -1)
		perror("child socket creating error \n");

	if (bind(s2, &sock2,sizeof(sock2))==-1)
			perror("child binding eror\n");

	if ((s1=socket(PF_UNIX, SOCK_DGRAM,0)) == -1)
		perror("parent socket creating error \n");

	if (bind(s1, &sock1,sizeof(sock1))==-1)
		perror("parent binding eror\n");

	sprintf(mesg0,"first");	

	if (sendto(s1, mesg0, sizeof(mesg0),0, &sock2,sizeof(sock2))==-1)
		perror("parent send error\n");

	if (fork()==0)
	{
		printf("child birth\n");

		if (recvfrom(s2, mesg2, sizeof(mesg2),0,&sock1,sizeof(sock1))==-1)
			perror("child receive error\n");

		printf("child receives mesg %s\n",mesg2);

		sprintf(mesg3,"child's messag");	

			if (sendto(s2, mesg3, sizeof(mesg3),0, &sock1,sizeof(sock1))==-1)
					perror("send error\n");
		
		exit(0);
	}

	printf("mother\n");

	if (recvfrom(s1, mesg4, sizeof(mesg4),0,&sock2, sizeof(sock2))==-1)
		perror("receive error\n");

	printf("%s\n",mesg2);

	wait(&ret);

	unlink(sock1.sa_data);
	unlink(sock2.sa_data);

	if (close(s1)==-1)
		perror("close error\n");
	if (close(s2)==-1)
		perror("close error\n");

}
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hung-Hsien Chang ( Hubert)		E-mail: hubert at cs.ucsb.edu

P.S: Hubert is not my middle name; it is easier for American friends to call me.