tcp-server.c

#include <ctype.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <signal.h>

#define SIZE sizeof(struct sockaddr_in)
#define MYPORT 7091
void catcher(int sig);
int newsockfd;

main()
{
   int sockfd;
   char c;
   struct sockaddr_in server = {AF_INET, MYPORT, INADDR_ANY};
   static struct sigaction act;

   act.sa_handler = catcher;
   sigfillset(&(act.sa_mask));
   sigaction(SIGPIPE, &act, NULL);

   if((sockfd=socket(AF_INET, SOCK_STREAM, 0)) == -1){
      perror("socket call failed");
      exit(1);
   }
   if(bind(sockfd, (struct sockaddr *)&server, SIZE) == -1){
      perror("bind call failed");
      exit(1);
   }
   if(listen(sockfd,5) == -1){
      perror("listen call failed");
      exit(1);
   }
   while(1){
      if((newsockfd=accept(sockfd, NULL, NULL)) == -1){
         perror("accept call failed");
         continue;
      }

      if(fork() == 0){
         while(recv(newsockfd, &c, 1, 0) > 0){
            c = toupper(c);
            send(newsockfd, &c, 1, 0);
         }
         close(newsockfd);
         exit(0);
      }

      close(newsockfd);
   }
}

void catcher(int sig)
{
   close(newsockfd);
   exit(0);
}