i want to write a daemon service which listens the 8080 port and write down all the details in one file. How can i do this ?
you must use 2 parts:
- tcp server
- fork() for daemonize your server
if you wish to use more than 1 tcp session from outside, than you must use fork() or pthread_create(). The pthread version is better (less memory and faster). Example code is some big, but you can find it in many places.
For go to daemon, you can use this code (create header for it and use toDaemon call):
//
// close all FDs >= a specified value
//
void
daemon::closeall(int fd) {
#ifndef SOLARIS
int fdlimit = sysconf(_SC_OPEN_MAX);
while(fd < fdlimit) close(fd++);
#endif //SOLARIS
}
// detach process from user and disappear into the background
// returns -1 on failure, but you can't do much except exit in that case
// since we may already have forked. This is based on the BSD version,
// so the caller is responsible for things like the umask, etc.
int
daemon::toDaemon(int nochdir, int noclose) {
switch(fork()) {
case 0:
break;
case -1:
return -1;
default:
_exit(0); // exit the original process
}
if(setsid() < 0) // shoudn't fail
return -1;
// dyke out this switch if you want to acquire a control tty in
// the future -- not normally advisable for daemons
switch(fork()) {
case 0:
break;
case -1:
return -1;
default:
_exit(0);
}
if(!nochdir) chdir("/");
if(!noclose) {
closeall(0);
open("/dev/null",O_RDWR);
dup(0); dup(0);
}
return 0;
}
// fork2() -- like fork, but the new process is immediately orphaned
// (won't leave a zombie when it exits)
// Returns 1 to the parent, not any meaningful pid.
// The parent cannot wait() for the new process (it's unrelated).
// This version assumes that you *haven't* caught or ignored SIGCHLD.
// If you have, then you should just be using fork() instead anyway.
int
daemon::fork2() {
pid_t pid;
int status;
if(!(pid = fork())) {
switch (fork()) {
case 0:
return 0;
case -1:
_exit(errno); // assumes all errnos are <256
default:
_exit(0);
}
}
if(pid < 0 || waitpid(pid,&status,0) < 0) return -1;
if(WIFEXITED(status)) {
if(WEXITSTATUS(status) == 0) return 1;
else errno = WEXITSTATUS(status);
} else {
errno = EINTR; // well, sort of 
}
return -1;
}