client server communication using sockets in c

/************************************************************************* * File : client-server-using-socketpair.c * Author : Saurabh Gupta * Desc : Client/Server Example Using socketpair(2) and fork(2) * Source : http://saurabhgupta0527.blogspot.com/2011/07/socket.html * Created : AM 07:27 21 September 2011 * Note : *************************************************************************/ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <time.h> #include <sys/types.h> #include <sys/socket.h> #include <sys/wait.h> /* * As of RedHat-6.0, these are still not defined */ #ifndef SHUT_WR #define SHUT_RD 0 #define SHUT_WR 1 #define SHUT_RDWR 2 #endif /* * Main program */ int main(int argc,char **argv) { int z; /* Status return code */ int s[2]; /* Pair of sockets */ char *msgp; /* A message pointer */ int mlen; /* Message length */ char buf[80]; /* Work buffer */ pid_t chpid; /* Child PID */ /* * Create a pair of local sockets */ z = socketpair(AF_LOCAL,SOCK_STREAM,0,s); if ( z == -1 ) { fprintf(stderr, "%s socketpair(2)\n", strerror(errno)); exit(1); } /* * Now fork() into two processes */ if ( (chpid = fork()) == (pid_t)-1 ) { /* * Failed to fork into two processes */ fprintf(stderr, "%s fork(2)\n", strerror(errno)); exit(1); } else if ( chpid == 0 ) { /* * This is the child process (client): */ char rxbuf[80]; /* Receive buffer */ printf ("Parent PID is %ld\n",(long)getppid()); close(s[0]); /* Server uses s[1] */ s[0] = -1; /* Forget this unit */ /* * Form the message and its length */ msgp = "%A %d-%b-%Y %l:%M %p"; mlen = strlen(msgp); printf("Child sending request '%s'\n",msgp); fflush(stdout); /* * Write a request to the server */ z = write(s[1],msgp,mlen); if ( z < 0 ) { fprintf(stderr, "%s write(2)\n", strerror(errno)); exit(1); } /* * Now indicate that we will not be writing * anything further to our socket, by shutting * down the write side of the socket */ if ( shutdown(s[1],SHUT_WR) == -1 ) { fprintf(stderr,"%s shutdown (2)\n", strerror(errno)); exit(1); } /* * Receive the reply from the server */ z = read(s[1],rxbuf,sizeof rxbuf); if ( z < 0 ) { fprintf(stderr,"%s read(2)\n", strerror(errno)); exit(1); } /* * Put a null byte at the end of what we * received from the server */ rxbuf[z] = 0; /* * Report the results */ printf("Server returned '%s'\n",rxbuf); fflush(stdout); close(s[1]); /* Close our end now */ } else { /* * This is the parent process (server): */ int status; /* Child termination status */ char txbuf[80]; /* Reply buffer */ time_t td; /* Current date & time */ printf ("Child PID is %ld\n", (long)chpid); fflush(stdout); close(s[1]); /* Client uses s[1] */ s[1] = -1; /* Forget this descriptor */ /* * Wait for a request from the client */ z = read(s[0],buf,sizeof buf); if ( z < 0 ) { fprintf(stderr,"%s read(2)\n", strerror(errno)); exit(1); } /* * Put a null byte at the end of the * message we received from the client */ buf[z] = 0; /* * Now perform the server function on the * received message */ time(&td); /* Get current time */ strftime(txbuf,sizeof txbuf, /* Buffer */ buf, /* Input format */ localtime(&td)); /* Input time */ /* * Send back the response to client */ z = write(s[0],txbuf,strlen(txbuf)); if ( z < 0 ) { fprintf(stderr,"%s write(2)\n", strerror(errno)); exit(1); } /* * Close our end of the socket */ close(s[0]); /* * Wait for the child process to exit. * See text. */ waitpid(chpid,&status,0); } return 0; } /* * OUTPUT * [sgupta@rhel55x86 socketpair]$ gcc client-server-using-socketpair.c -o client-server-using-socketpair [sgupta@rhel55x86 socketpair]$ ./client-server-using-socketpair Parent PID is 10622 Child sending request '%A %d-%b-%Y %l:%M %p' Child PID is 10623 Server returned 'Wednesday 21-Sep-2011 8:53 AM' [sgupta@rhel55x86 socketpair]$ */

See Also:

Socket Tutorial and Sample Codes

Advance Socket Tutorial and Sample Code