linux socket编程 daemon例子

#include <stdarg.h>
#include <stdio.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <signal.h>
#include <sys/wait.h>
#include <syslog.h>
#include <sys/ioctl.h>
#include <fcntl.h>
typedef void (*Sigfunc)(int);

void reap_status() {
int pid;
int status;
while((pid = wait3(&status, WNOHANG, NULL)>0));
}

void daemon_init(int s) {
int childpid, fd, fdtablesize;
int ret;
signal(SIGTTOU,SIG_IGN);
signal(SIGTTIN,SIG_IGN);
signal(SIGTSTP,SIG_IGN);
childpid=fork();
if(childpid == -1)
error(1,errno,"fork error!");
else if(childpid >0)
exit(0);

if(setsid()== -1)
error(1,0,"setsid error!");

childpid=fork();
if(childpid == -1)
error(1,errno,"fork error!");
else if(childpid >0)
exit(0);
/*
if(setpgrp(0,getpid())<0)
error(1,0,"setpgrp error!");
if((fd = open("/dev/tty",O_RDWR))>0){
ioctl(fd,TIOCNOTTY,NULL);
close(fd);
}
*/
for(fd=0, fdtablesize = getdtablesize(); fd < fdtablesize; fd++)
if(s != fd)
close(fd);
chdir("/");
umask(0);
signal(SIGCLD, (Sigfunc)reap_status);
openlog("hello",LOG_PID,0);
}

void process_server(int s, struct sockaddr_in * remote) {
char buff[128];
int len;
send(s, "hello/n!", 6, 0);
}

int main(int argc, char **argv) {
struct sockaddr_in remote;
char *hname, *sname;
int s, c, len;
if(argc < 2)
error(1,0,"parameters less than 2");
else if(argc == 2) {
hname = NULL;
sname = argv[1];
}
else if(argc == 3) {
hname = argv[1];
sname = argv[2];
}
s = server(hname, sname,"tcp");
daemon(s);
len = sizeof(struct sockaddr);
while(1) {
if((c=accept(s,(struct sockaddr *)&remote,&len))<=0)
error(1,errno,"accept error!");
process_server(c,&remote);
}
close(s);
close(c);
exit(0);
}