Linux under C programming: socket instance

Client:

#include <stdio.h> #include <sys/socket.h> #include <unistd.h> #include <sys/types.h&     
Gt #include <netinet/in.h> #include <stdlib.h> #define SERVER_PORT 20000//define the Defualt con      
Nect Port ID #define CLIENT_PORT ((20001+rand ())%65536)//define the Defualt CLIENT port as a random port  #define BUFFER_SIZE 255 #define REUQEST_MESSAGE "Welcome to connect the server.\n" void     
Usage (char* name) {printf ("Usage:%s ipaddr\n", name);     
       int main (int argc, char** argv) {int servfd,clifd,length = 0;     
       struct sockaddr_in servaddr,cliaddr;     
       socklen_t Socklen = sizeof (SERVADDR);     
         
        Char Buf[buffer_size];     
              if (ARGC < 2) {usage (argv[0]);     
       Exit (1); } if ((CLIFD = socket (af_inet,sock_stream, 0)) < 0) {printf ("Create socket error!\n");     
       Exit (1); } Srand (Time (NULL));     
       Initialize Random generator bzero (& cliaddr, sizeof (CLIADDR));     
       cliaddr.sin_family = af_inet;     
       Cliaddr.sin_port = htons (Client_port);     
         
       CLIADDR.SIN_ADDR.S_ADDR = htons (Inaddr_any);     
       Bzero (& servaddr, sizeof (SERVADDR));     
       servaddr.sin_family = af_inet;     
       Inet_aton (argv[1], & SERVADDR.SIN_ADDR);     
      Servaddr.sin_port = htons (Server_port);      
         
       SERVADDR.SIN_ADDR.S_ADDR = htons (Inaddr_any); if (Bind (CLIFD, (struct sockaddr*) &cliaddr, sizeof (CLIADDR)) < 0) {printf ("b     
              IND to port%d failure!\n ", client_port);     
       Exit (1); } if (Connect (CLIFD, (struct sockaddr *) & Servaddr, Socklen) < 0)     
              {printf ("can ' t connect to%s!\n", argv[1]);     
       Exit (1);     
        Length = recv (CLIFD, buf, buffer_size, 0); if (length < 0) {printf ("error comes when recieve data from server%s!", argv[1])     
              ;     
       Exit (1);     
         
       printf ("From server%s: \n\t%s", argv[1], buf);     
       Close (CLIFD);     
return 0; }

Server-side:

#include <stdio.h> #include <sys/socket.h> #include <unistd.h> #include <sys/t      
          
ypes.h> #include <netinet/in.h> #include <stdlib.h> #include <time.h> #define SERVER_PORT 20000//define the Defualt connect PORT ID #define LENGTH_OF_LISTEN_QUEUE/len Gth of Listen queue in server #define BUFFER_SIZE 255 #define Welcome_message ' WELCOME to connect the server .     
       int main (int argc, char** argv) {int servfd,clifd;     
         
       struct sockaddr_in servaddr,cliaddr; if ((servfd = socket (af_inet,sock_stream, 0)) < 0) {printf ("Create socket E     
              Rror!\n ");     
       Exit (1);     
         
       Bzero (& servaddr, sizeof (SERVADDR));     
       servaddr.sin_family = af_inet; Servaddr.sin_port = htons (server_poRT);     
         
       SERVADDR.SIN_ADDR.S_ADDR = htons (Inaddr_any); if (bind (servfd, struct sockaddr *) & servaddr, sizeof (SERVADDR)) < 0) {pri     
              NTF ("Bind to Port%d failure!\n", server_port);     
       Exit (1); } if (Listen (Servfd,length_of_listen_queue) < 0) {print     
              F ("Call listen failure!\n");     
       Exit (1);      
         
              while (1) {//server loop would nerver exit unless any body kill the process     
              Char Buf[buffer_size];     
              Long timestamp;     
              socklen_t length = sizeof (CLIADDR);     
         
               CLIFD = Accept (servfd, struct sockaddr *) & cliaddr, & length); if (Clifd < 0) {printf ("error comes when call accept!\n");
                     break;

               } strcpy (Buf,welcome_message);

              Inet_ntop (inet_addrstrlen,cliaddr.sin_addr,buf,buffer_size);

              printf ("From client,ip:%s,port:%d\n", Inet_ntoa (CLIADDR.SIN_ADDR), Ntohs (Cliaddr.sin_port));

              Timestamp = time (NULL); 
              strcat (buf, "timestamp in server:");

              Strcat (Buf,ctime (& timestamp)); 

              Send (clifd,buf,buffer_size, 0);                

       Close (CLIFD);     

        }//Exit Close (SERVFD);     
return 0; }

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