Hello guys,

I m working on a chat program with C. I finished the iterative server and it's working well. But once I add fork(), I met problems. I cannot use close or exit, otherwise I cannot accept new connection in next loop. here is my code:

.
.
.
Listen(simpleSocket, 5);

signal(SIGCHLD, sigchld_handler);

/*****************************************************************/
while (1)
{
int tmpSock = 0;
int pid;
char buf[200] = "";
sendPack sp; /*struct traveling btw 3 programs*/
struct sockaddr_in clientName = { 0 };
int clientNameLength = sizeof(clientName);
int valUsr = 0, i = 0, status = 0;

/* wait here */
/*************************************************************/
simpleChildSocket = Accept(simpleSocket,
(struct sockaddr *)&clientName, &clientNameLength);
/*************************************************************/

if((pid = fork()) == 0)
{
/*if I close listen socket here, parent process cannot accept connection next time*/
close(simpleSocket);

returnStatus = Read(simpleChildSocket, &sp,
sizeof(sp));

if(sp.flag == 1)
{
/* printf("here we go: %s\n", sp.usrName); */
login(sp.usrName, simpleChildSocket, usrHead);

}
else if(sp.flag == 2)
{
if((tmpSock = judgeUser(usrHead, sp.usrName)))
{
status = 1;
Write(simpleChildSocket, &status, sizeof(int));
printf("Pass judgeUser.\n");
returnStatus = read(simpleChildSocket, &sp,
sizeof(sp));

if ( returnStatus > 0 ) {
printf("%d: %s", returnStatus, sp.usrName);
} else {
fprintf(stderr, "Return Status = %d \n", returnStatus);
}
while(sp.func != 4)
{
/*judge val of returnStatus inside func.*/
if(returnStatus > 0)
{
printf("Switch start..\n");
switch(sp.func)
{
case 1:
printf("Single send server.\n");
relaySingle(sp, usrHead, simpleChildSocket);
break;
case 2:
relayGroup(sp, usrHead, simpleChildSocket);
break;
case 3:
queryUsr(usrHead, simpleChildSocket);
break;
default :
break;
}

}
memset(&sp, '\0', sizeof(sp));
returnStatus = Read(simpleChildSocket, &sp,
sizeof(sp));
}
/*Delete quitting usrName.*/
sendQuit(usrHead, sp.usrName);
Write(tmpSock, &sp, sizeof(sp));
}
else
{
printf("You have not logged in yet.\n");
Write(simpleChildSocket, &status, sizeof(int));
}
}

/*If I use exit(0) or close child socket here, parent process cannot accept connection next time.*/
close(simpleChildSocket);
exit(0);
}

}

close(simpleSocket);
return 0;

}

could you please check once again that in the forking part
(pid_t = fork () ) == 0
/* child */
pid_t > 0
you dont call exit by mistake...

i have not gone through completely ...

if your accept is failing what is the errno?

Thanku matrixmadhan,

It can accept connection before using fork(), but cause error at 2rd time. the error msg is :

In function Accept() :
accept() : returned -1, errno=EINTR (Interrupted system call)
parameters : s = 3
addr = ffbff4b8
addrlen = ffbff4b4
(*addrlen = 16 before call, 16 after call)
From the man page:
accept() will fail if:
EINTR The accept attempt was interrupted by
the delivery of a signal.



Cheers,

Elton

For simple stream server stub look at http://beej.us/guide/bgnet/output/ht...l#simpleserver