socklib.h
1 int make_server_socket(int );2 int connect_to_server(char* , int );3 int process_request(int );4 int talk_with_server(int );

  1 /* socklib.c  2  * This file contains functions used lots when writing internet  3  * client/ server programs.    The two main functions here are:  4  *   5  * int make_server_socket(portnum) returns a server socket   6  *                                       or -1 if error  7  * int make_server_socket_q(portnum, backlog)  8  *   9  * int connect_to_server(char* hostname, int portnum) return a connected socket 10  *                                       or -1 if error 11  */ 12 #include <stdio.h> 13 #include <unistd.h> 14 #include <sys/socket.h> 15 #include <sys/types.h> 16 #include <netinet/in.h> 17 #include <netdb.h> 18 #include <time.h> 19 #include <strings.h> 20  21 #define HOSTLEN 256 22 #define BACKLOG 1 23 #define oops(msg) {perror(msg); exit(1);} 24  25 int make_server_socket_q(int , int); 26  27 int make_server_socket(int portnum) { 28   return make_server_socket_q(portnum, BACKLOG); 29 } 30  31 int make_server_socket_q(int portnum, int backlog) { 32   struct sockaddr_in saddr; 33   struct hostent *hp; 34   char hostname[HOSTLEN]; 35   int sock_id; 36   sock_id=socket(PF_INET, SOCK_STREAM, 0); 37   if(sock_id == -1) 38     return -1; 39   /*bulid socket bind*/ 40   bzero((void*)&saddr, sizeof(saddr)); 41   gethostname(hostname, HOSTLEN); 42   hp=gethostbyname(hostname); 43    44   bcopy((void*)hp->h_addr, (void*)&saddr.sin_addr, hp->h_length); 45   saddr.sin_port=htons(portnum); 46   saddr.sin_family=AF_INET; 47   if(bind(sock_id, (struct sockaddr*)&saddr, sizeof(saddr))!=0) 48     return -1; 49  50   /** arrange for incoming calls **/ 51   if(listen(sock_id, backlog)!=0) 52     return -1; 53   return sock_id; 54 } 55  56 int connect_to_server(char *host, int portnum) { 57   int sock; 58   struct sockaddr_in servadd; 59   struct hostent *hp; 60   /** Step1: get a socket**/ 61   sock=socket(AF_INET, SOCK_STREAM, 0); 62   if(sock==-1) 63     return -1; 64   /**Step2: connect to server**/ 65   bzero((void*)&servadd, sizeof(servadd)); 66   hp=gethostbyname(host); 67   if(hp==NULL) 68     return -1; 69   bcopy(hp->h_addr, (struct sockaddr*)&servadd.sin_addr, hp->h_length); 70   servadd.sin_port=htons(portnum); 71   servadd.sin_family=AF_INET; 72   if(connect(sock, (struct sockaddr* )&servadd, sizeof(servadd))!=0) 73     return -1; 74   return sock;  75 } 76  77 int talk_with_server(int fd) { 78   char buf[BUFSIZ]; 79   int len; 80   len = read(fd, buf, BUFSIZ); 81   if(len==-1) 82     return -1; 83   if(write(1, buf, len)!=len) 84     return -1; 85   return 0; 86 } 87 /* 88 int process_request(int fd) { 89   time_t thetime; 90   char *cp; 91   time(&thetime); 92   cp=ctime(&thetime); 93   if(write(fd, cp, strlen(cp)) != strlen(cp)) 94     return -1; 95   return 0; 96 } 97 */ 98 int process_request(int fd) { 99   int pid = fork();100   switch(pid) {101   case -1: return -1;102   case 0: dup2(fd, 1);103     close(fd);104     execl("/bin/date", "date", NULL);105     oops("execl");106   default:wait(NULL);107   }108 }

/* timeclnt_new.c - a new client for use the socklib.c */#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <netdb.h>#include <time.h>#include <strings.h>#include "socklib.h"#define oops(msg) {perror(msg); exit(1);}int main(int argc, char* argv[]){  int sock_id;  sock_id=connect_to_server(argv[1],atoi(argv[2]));  if(sock_id==-1)    oops("connect_to_server");  if(talk_with_server(sock_id) == -1)    oops("talk_to_server");  close(sock_id);  return 0;}

 1 #include <stdio.h> 2 #include <unistd.h> 3 #include <sys/types.h> 4 #include <sys/socket.h> 5 #include <netinet/in.h> 6 #include <netdb.h> 7 #include <time.h> 8 #include <strings.h> 9 #include "socklib.h"10 11 #define oops(msg){ perror(msg); exit(1);}12 #define PORTNUM 1300013 int main(void ) {14   int sockid, fd;15   sockid=make_server_socket(PORTNUM);16   if(sockid==-1)17     oops("make_server_socket");18   while(1){19     fd=accept(sockid, NULL, NULL);20     if(fd==-1)21       break;22     process_request(fd);23     close(fd);24   }25   return 0;26 }