Linux TCP/IP network programming (multi-process)

 

Multi-process network programming example:

# Include <stdio. h> # include <errno. h> # include <netdb. h> # include <sys/socket. h> // may be use by getpid () and getppid () # include <unistd. h> int main (int argc, char * argv []) {int sockfd, new_fd, mypid; struct sockaddr_in server_addr; struct sockaddr_in client_addr; int sin_size, portnumber; char hello [] = "Hello! Are You Fine? "; Char buf [1024]; int flag; if (argc! = 2) {fprintf (stderr, "Usage: % s portnumber \ a \ n", argv [0]); exit (1 );} if (portnumber = atoi (argv [1]) <0) {fprintf (stderr, "Usage: % s portnumber \ a \ n", argv [0]); exit (1);}/* the server starts to establish the socket descriptor */if (sockfd = socket (AF_INET, SOCK_STREAM, 0) =-1) {fprintf (stderr, "Socket error: % s \ n \ a", strerror (errno); exit (1);}/* fill the sockaddr structure on the server */bzero (& server_addr, sizeof (struct sockaddr_in); server_addr.sin_family = AF _ INET; struct = htonl (INADDR_ANY); server_addr.sin_port = htons (portnumber);/* bind the sockfd descriptor */if (bind (sockfd, (struct sockaddr *) (& server_addr ), sizeof (struct sockaddr) =-1) {fprintf (stderr, "Bind error: % s \ n \ a", strerror (errno); exit (1 );} /* listen to the sockfd descriptor */if (Listen (sockfd, 5) =-1) {fprintf (stderr, "listen error: % s \ n \ ", strerror (errno); exit (1);} // printf my PID num printf ("Sta Rting Server at port: % d Success. my PID is: % d \ nAccepting Request... \ n ", portnumber, getpid (); while (1) {/* server blocking until the Client Program establishes a connection */sin_size = sizeof (struct sockaddr_in ); if (new_fd = accept (sockfd, (struct sockaddr *) (& client_addr), & sin_size) =-1) {fprintf (stderr, "Accept error: % s \ n \ a ", strerror (errno); exit (1) ;}// generate a sub-process to complete the session with the client. The parent process continues to listen to if (! Fork () {// print my PID and my parent PID mypid = getpid (); printf ("Accepting new connection... \ nNow I will server for you. my PID is: % d \ nMy parent PID is: % d \ n ", mypid, getppid (); // subprocess, close the parent process listening socket close (sockfd ); fprintf (stderr, "Server get connection from % s \ n", inet_ntoa (client_addr.sin_addr); if (write (new_fd, hello, strlen (hello) =-1) {fprintf (stderr, "Write Error: % s \ n", strerror (errno); exit (1) ;}while (1) // get data from client {if (flag = read (new_fd, buf, 1024) <0) {printf ("Reading data error"); break ;} if (flag = 0) {printf ("[PID: % d] Ending current connection \ n", mypid); break;} else {printf ("[PID: % d] --> % s \ n ", mypid, buf); if (strstr (buf," exit ") {printf (" I get 'exit 'string, so close client connection \ n "); break ;}}// end while (get data from client) // The connection is lost and the process ends (the customer proactively disconnects, automatic disconnection due to network problems) printf ("Connection lose. end child program, PID: % d \ n ", getpid (); close (new_fd); exit (0) ;}// if fork // The parent process closes the new socket, continue listening for request close (new_fd);} // while close (sockfd); exit (0 );}

: