Linux Socket 学习笔记3–实现一个简单的C/S程序

/*
**   Client/Server Example Using socketpair(2)
*/
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include    
 
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));
        return 1;   //create socket failed
    }
 
    //Now fork() into two processes :
    if ( (chpid = fork()) < 0 )
    {
        fprintf(stderr,"%s: fork(2)n",strerror(errno));
        return 2;   //Failed to fork
    }
    else if ( chpid == 0 )
    {
        /*
       * This is the child process (client) :
       */
        char rxbuf[80]; /* Receive buffer */
        printf("Parent PID is %ldn",(long)getppid());
        close(s[0]);    /* Server uses s[0] */
        s[0] = -1;      /* Forget this unit */
 
        msgp = "%A %d-%b-%Y %l:%M %p";  //client message
        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));
            return 3;   //write failed;
        }
 
        /*
       * 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));
            return 4;   //shutdown failed
        }
 
       // Receive the reply from the server :
        z = read(s[1],rxbuf,sizeof(rxbuf));
        if ( z < 0 )
        {
            fprintf(stderr,"%s: read(2)n",strerror(errno));
            return 5;   //read failed
        }
 
        rxbuf[z] = 0;
        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 %ldn",(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,buf,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));
            return 6;       //server write failed
        }
    close(s[0]);
 
    // Wait for the child process to exit..
    waitpid(chpid,&status,0);
    }
    return 0;
}