Programming

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


#define SERVER_PORT 12345
#define BUF_SIZE 4096


int main(int argc, char *argv[])
{
  int sock;
  int connection;
  int message_sent;
  int message_rec;
  char user_data[BUF_SIZE];
  char host_reply[BUF_SIZE];
  char *ip_server;
  char *string_name;
  char datagram[4096];
  struct sockaddr_in ip_address;

  ip_server = argv[1];
  string_name = argv[2];


  // Constructing TCP Header
  struct tcphder {
    char type;
    int reserve1;
    short reserve2;
    int len;
    int sequence;
    char *data;
  };
  
  memset (datagram, 0, 4096);

  struct tcphder *tcph = (struct tcphder *)datagram;

  tcph->data = argv[2];
  tcph->sequence = random();
  tcph->len = strlen(argv[2]);
  tcph->reserve1 = 0;
  tcph->reserve2 = 0;
  tcph->type = '8';

  if (argc != 3)
  {
    fprintf(stderr, "Usage: %s <Server IP Address> <Message>\n", argv[0]);
    exit(1);
  }


// Create a communication point
  sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);

  if (sock < 0)
  {
    fprintf(stderr, "socket error.\n");
    exit(1);
  }


// Build server adress structure
  memset(&ip_address, 0, sizeof(ip_address));
  ip_address.sin_family=AF_INET;
  ip_address.sin_addr.s_addr=inet_addr(ip_server);
  ip_address.sin_port=htons(SERVER_PORT);

// Make connection to server
  connection = connect(sock, (struct sockaddr *) &ip_address, sizeof(ip_address));

  if (connection < 0)
  {
    fprintf(stderr, "connect error.\n");
    exit(1);
  }


  // Send entered data to server
  message_sent = send(sock, datagram, tcph->len, 0);

  message_rec = recv(sock, host_reply, 1024, 0);
  host_reply[message_rec] = '\0';

  printf("Reply from server: %s\n", host_reply);

close(sock);
exit(1);

}

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


#define SERVER_PORT 12345
#define BUFFER_SIZE 4096
#define MAX_CONNECT 5


int main(int argc, char *argv[])
{
   int sock_server;
   int sock_client;
   int on=1;
   int binding;
   int listening;
   int message_rec;
   int message_sent;
   char buffer_size[BUFFER_SIZE];
   char message_client[1024];
   socklen_t len;
   struct sockaddr_in ip_address_server;
   struct sockaddr_in ip_address_client;



// Create socket for incomming connection
   sock_server = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

  if (sock_server < 0)
  {
 fprintf(stderr, "socket error\n");
    exit(1);
  }


// Build server address structure
   memset(&ip_address_server, 0, sizeof(ip_address_server));
   ip_address_server.sin_family = AF_INET;
   ip_address_server.sin_addr.s_addr = htonl(INADDR_ANY);
   ip_address_server.sin_port = htons(SERVER_PORT);
   setsockopt(sock_server, SOL_SOCKET, SO_REUSEADDR, (char *) &on,   sizeof(on));


// Attach a local address to a socket
   binding = bind(sock_server, (struct sockaddr *) &ip_address_server, sizeof(ip_address_server));

  if (binding != 0)
  {
    fprintf(stderr, "bind error\n");
    exit(1);
  }


// Listen for connection
   listening = listen(sock_server, MAX_CONNECT);
   printf ("listening");
  if (listening != 0)
  {
    fprintf(stderr, "listen error\n");
    exit(1);
  }
while (1)
{

   // Accept client connection
   sock_client = accept(sock_server, &ip_address_client, &len);

   // Get message from client
   message_rec = recv(sock_client, buffer_size, BUFFER_SIZE, 0);   
   buffer_size[message_rec] = '\0';

   // Send message back to client
   message_sent = send(sock_client, buffer_size, strlen(buffer_size), 0);


}
   close(sock_client);

}