#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define BUF_SIZE 1024

int main(int argc, char* argv[])
{
   int nSocket;
   int nConnect;
   int nBytes;
   struct sockaddr_in stServerAddr;
   struct hostent* lpstServerEnt;
   char cbBuf[BUF_SIZE];

   if (argc != 3)
   {
     fprintf(stderr, "Usage: %s server_name port_number\n", argv[0]);
     exit(1);
   }

   /* look up server's IP address */
   lpstServerEnt = gethostbyname(argv[1]);
   if (! lpstServerEnt)
   {
      fprintf(stderr, "%s: Can't get the server's IP address.\n", argv[0]);
      exit(1);
   }

   /* create a socket */
   nSocket = socket(PF_INET, SOCK_STREAM, 0);
   if (nSocket < 0)
   {
      fprintf(stderr, "%s: Can't create a socket.\n", argv[0]);
      exit(1);
   }

   /* server info */
   memset(&stServerAddr, 0, sizeof(struct sockaddr));
   stServerAddr.sin_family = AF_INET;
   memcpy(&stServerAddr.sin_addr.s_addr, lpstServerEnt->h_addr, lpstServerEnt->h_length);
   stServerAddr.sin_port = htons(atoi(argv[2]));

   /* connect to the server */
   nConnect = connect(nSocket, (struct sockaddr*)&stServerAddr, sizeof(struct sockaddr));
   if (nConnect < 0)
   {
      fprintf(stderr, "%s: Can't connect to the server (%s:%i).\n", argv[0], argv[1], atoi(argv[2]));
      exit(1);
   }

   /* connection is now established; read from socket */
   nBytes = read(nSocket, cbBuf, BUF_SIZE);
   write(1, cbBuf, nBytes);

   close(nSocket);
   return 0;
}

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define SERVER_PORT 1234
#define QUEUE_SIZE 5

void childend(int signo)
{
   pid_t pid;
   pid = wait(NULL);
   printf("\t[end of child process number %d]\n", pid);
}

int main(int argc, char* argv[])
{
   int nSocket, nClientSocket;
   int nBind, nListen;
   int nFoo = 1, nTmp;
   struct sockaddr_in stAddr, stClientAddr;

   signal(SIGCHLD, childend);

   /* address structure */
   memset(&stAddr, 0, sizeof(struct sockaddr));
   stAddr.sin_family = AF_INET;
   stAddr.sin_addr.s_addr = htonl(INADDR_ANY);
   stAddr.sin_port = htons(SERVER_PORT);

   /* create a socket */
   nSocket = socket(AF_INET, SOCK_STREAM, 0);
   if (nSocket < 0)
   {
       fprintf(stderr, "%s: Can't create a socket.\n", argv[0]);
       exit(1);
   }
   setsockopt(nSocket, SOL_SOCKET, SO_REUSEADDR, (char*)&nFoo, sizeof(nFoo));

   /* bind a name to a socket */
   nBind = bind(nSocket, (struct sockaddr*)&stAddr, sizeof(struct sockaddr));
   if (nBind < 0)
   {
       fprintf(stderr, "%s: Can't bind a name to a socket.\n", argv[0]);
       exit(1);
   }

   /* specify queue size */
   nListen = listen(nSocket, QUEUE_SIZE);
   if (nListen < 0)
   {
       fprintf(stderr, "%s: Can't set queue size.\n", argv[0]);
   }

   while(1)
   {
       /* block for connection request */
       nTmp = sizeof(struct sockaddr);
       nClientSocket = accept(nSocket, (struct sockaddr*)&stClientAddr, &nTmp);
       if (nClientSocket < 0)
       {
           fprintf(stderr, "%s: Can't create a connection's socket.\n", argv[0]);
           exit(1);
       }

       /* connection */
       if (! fork())
       {
           printf("%s: [connection from %s]\n",
                  argv[0], inet_ntoa((struct in_addr)stClientAddr.sin_addr));
           write(nClientSocket, "Hello World!\n", 13);
           close(nClientSocket);
           exit(0);
       }
   }

   close(nSocket);
   return(0);
}