TCP client - server

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1 zombie process

Signal processing

 

signal:

1 by a process destined for another process

2 sent to a process by the kernel

 

Zombie state:

Resource ID information retrieval parent process child process, process, end state, the child's use of information

 

When programming:

1 When spawn child process must be captured signal SIGCHLD

2 When capturing signal processing must be interrupted system call

3 SIGCHLD signal handler must be written correctly, use the function waitpid to avoid leaving a zombie process

 

 1 int main(int argc,char **argv){
 2 int listenfd,connfd;
 3 pid_t childpid;
 4 socklen_t clilen;
 5 struct sockaddr_in cliaddr,servaddr;
 6 void sig_chld(int);
 7  
 8 listenfd = Socket(AF_INET,SOCK_STREAM,0);
 9     
10 bzero(&servaddr,sizeof(servaddr));
11 servaddr.sin_family = AF_INET;
12 servaddr.sin_addr.s_addr = htol(INADDR_ANY);
13 servaddr.sin_port = htons(SERV_PORT);
14  
15 Bind(listenfd,(SA *)&servaddr,sizeof(servaddr));
16 Listen(listendfd,LISTENQ);
17 Signal(SIGCHLD,sig_chld);
18 for(;;){
19     clilen = sizeof(cliaddr);
20     if((connfd = accept(listenfd,(SA *)&cliaddr,&clilen)) < 0){
21         if(errno == EINTR)
22             continue;
23         else
24             err_sys("accept error");
25     }
26     if((childpod = Fork()) == 0){
27         Close(listenfd);
28         str_echo(connfd);
29         exit(0);
30     }
31     Close(connfd);
32 }
33 }

 

Reproduced in: https: //my.oschina.net/u/204616/blog/544968