TCP

<server.c>

#include <stdio.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#include <signal.h>

#define SERV_PORT 62000
#define RECV_BUF_LEN 80

void sig_alrm(int signo);

void sig_alrm(int signo)
{

 printf("alarm...\n");

}

void sig_child(int signo)
{

 printf("Client terminated \n");

}

int main(int argc, char *argv[])
{

 int sfd, cfd;
 struct sockaddr_in saddr;
 struct sockaddr_in caddr;
 int size, len;
 char recv_buf[RECV_BUF_LEN];

 pid_t pid;

 sfd = socket(AF_INET, SOCK_STREAM, 0);
 len = sizeof(saddr);

 bzero((char*)&saddr, sizeof(saddr));
 saddr.sin_family = AF_INET;
 saddr.sin_addr.s_addr = htonl(INADDR_ANY);
 saddr.sin_port = htons(SERV_PORT);

 if ( bind(sfd, (struct sockaddr*)&saddr, sizeof(saddr)) < 0 ) {

  printf("Bind Error\n");
  return -1;

 }

 listen(sfd, 5);

 signal(SIGALRM, sig_alrm); 
 signal(SIGCHLD, sig_child); 
 //signal(SIGINT, SIG_IGN); //ignore 
 size = sizeof(caddr);

 while (1)
 {

  cfd = accept(sfd, (struct sockaddr*)&caddr, &size);//connect
  printf("Client : %d\n", cfd);

  pid = fork(); // call pre-fork() function

  if(pid <0)
  {
   printf("Fork Error!!\n");
   exit(-1);

  }

  else if(pid==0) //child process
  {

  // alarm(3);
   while(len = read(cfd, recv_buf, RECV_BUF_LEN))
   {

    recv_buf[len] = '\0';
    printf("recv : %s", recv_buf);
    

    if(strncmp(recv_buf, "exit",4) == 0)//client request termination.
    { 

//     close(cfd);
//     close(sfd);
//     return 0;
     exit(1);

    }         // alarm(0);

  else//parent process
  {
  }

 }

}

}

 close(cfd);
 close(sfd);

 return 0;

}

---

<client.c>

#include <stdio.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#define SERV_PORT 62000
#define RECV_BUF_LEN 1024
#define MSG_SIZE 1024

int main(int argc, char *argv[])
{

 int sfd;
 struct sockaddr_in saddr;
 int len, msglen;
 static char msg[MSG_SIZE];

 sfd = socket(AF_INET, SOCK_STREAM, 0);

 bzero((char*)&saddr, sizeof(saddr));
 saddr.sin_family = AF_INET;
 saddr.sin_addr.s_addr = inet_addr(argv[1]);
 saddr.sin_port = htons(SERV_PORT);

 if (connect(sfd, (struct sockaddr*)&saddr, sizeof(saddr)) < 0) {

  printf("connect error\n");
  return -1;

 }

 while (1)
{

  msglen = read(STDIN_FILENO, msg, MSG_SIZE);

  if (len = write(sfd, msg, msglen) < msglen)
{

   printf("write error\n");

  }

  if (strncmp(msg, "exit", 4) == 0)
  {

   close(sfd);
   return 0;

  }

 }

// close(sfd);

 return 0;

}