[QUestion] tcp client and server

silentkill89 · 09-04-2011, 11:35 AM

Actually I just want to know about how the tcp client respond before the tcp server able to respond in the first place. For example, in same computer, i ran 2 files, which is tcpserver.c and tcpclient.c
once they were both connected, server will ask like this "Send "q" or 'Q" to quit"

here is the chat begin, typing q to exit the program)
but i want to make the asking start from the client side instead of the server first. It's like a vice versa,but it stil can communicate with each other.

Code:

/* tcpserver.c */

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


int main()
{
        int sock, connected, bytes_recieved , true = 1;  
        char send_data [1024] , recv_data[1024];       

        struct sockaddr_in server_addr,client_addr;    
        int sin_size;
        
        if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
            perror("Socket");
            exit(1);
        }

        if (setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,&true,sizeof(int)) == -1) {
            perror("Setsockopt");
            exit(1);
        }
        
        server_addr.sin_family = AF_INET;         
        server_addr.sin_port = htons(5000);     
        server_addr.sin_addr.s_addr = INADDR_ANY; 
        bzero(&(server_addr.sin_zero),8); 

        if (bind(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr))
                                                                       == -1) {
            perror("Unable to bind");
            exit(1);
        }

        if (listen(sock, 5) == -1) {
            perror("Listen");
            exit(1);
        }
		
	printf("\nTCPServer Waiting for client on port 5000");
        fflush(stdout);


        while(1)
        {  

            sin_size = sizeof(struct sockaddr_in);

            connected = accept(sock, (struct sockaddr *)&client_addr,&sin_size);

            printf("\n I got a connection from (%s , %d)",
                   inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port));

            while (1)
            {
              printf("\n SEND (q or Q to quit) : ");
              gets(send_data);
              
              if (strcmp(send_data , "q") == 0 || strcmp(send_data , "Q") == 0)
              {
                send(connected, send_data,strlen(send_data), 0); 
                close(connected);
                break;
              }
               
              else
                 send(connected, send_data,strlen(send_data), 0);  

              bytes_recieved = recv(connected,recv_data,1024,0);

              recv_data[bytes_recieved] = '\0';

              if (strcmp(recv_data , "q") == 0 || strcmp(recv_data , "Q") == 0)
              {
                close(connected);
                break;
              }

              else 
              printf("\n RECIEVED DATA = %s " , recv_data);
              fflush(stdout);
            }
        }       

      close(sock);
      return 0;
}

Code:

/* tcpclient.c */

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


int main()

{

        int sock, bytes_recieved;  
        char send_data[1024],recv_data[1024];
        struct hostent *host;
        struct sockaddr_in server_addr;  

        host = gethostbyname("127.0.0.1");

        if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
            perror("Socket");
            exit(1);
        }

        server_addr.sin_family = AF_INET;     
        server_addr.sin_port = htons(5000);   
        server_addr.sin_addr = *((struct in_addr *)host->h_addr);
        bzero(&(server_addr.sin_zero),8); 

        if (connect(sock, (struct sockaddr *)&server_addr,
                    sizeof(struct sockaddr)) == -1) 
        {
            perror("Connect");
            exit(1);
        }

        while(1)
        {
        
          bytes_recieved=recv(sock,recv_data,1024,0);
          recv_data[bytes_recieved] = '\0';
 
          if (strcmp(recv_data , "q") == 0 || strcmp(recv_data , "Q") == 0)
          {
           close(sock);
           break;
          }

          else
           printf("\nRecieved data = %s " , recv_data);
           
           printf("\nSEND (q or Q to quit) : ");
           gets(send_data);
           
          if (strcmp(send_data , "q") != 0 && strcmp(send_data , "Q") != 0)
           send(sock,send_data,strlen(send_data), 0); 

          else
          {
           send(sock,send_data,strlen(send_data), 0);   
           close(sock);
           break;
          }
        
        }   
return 0;
}

Im still learning in socket programming, i just need some guidances and examples will do. Thank you

silentkill89 · 09-04-2011, 11:59 AM

Please help me, im urgently need help

tbrand · 09-04-2011, 12:29 PM

If I understand your question you want the client send some data before the server.

All you need to do is switch the order of reading and writing on the socket in the client and server.

After the client connects (connect()) it should write to the socket and then wait for response.

The server should first read the socket after it comes out of the accept().

You may also need to arrange for some protocol between the client and server indicating end of data or length of data. TCP connection is a data stream and the recv() function only tells you how much data it received not that its all the data.

Tinkster · 09-04-2011, 12:35 PM

Quote:

Originally Posted by silentkill89

Please help me, im urgently need help

Mate ... this is a forum where volunteers spend their
own unpaid for time supporting others. Don't badger,
and don't bounce your own thread, specially not
after having patiently waited all of 20 minutes.

Read our rules again.

Cheers,
Tink

P.S.: This is better off in programming, and I'm moving it across.

silentkill89 · 09-04-2011, 01:03 PM

Tbrand, i get what you mean, i have tried to switch the reading and writing order,but somehow it just messed up and the whole program gones wrong. Could you kindly show me which part of the client server program i can adjust because i need to get a clear idea on what's going around. Thank you

ta0kira · 09-04-2011, 01:54 PM

Quote:

Originally Posted by silentkill89

Tbrand, i get what you mean, i have tried to switch the reading and writing order,but somehow it just messed up and the whole program gones wrong. Could you kindly show me which part of the client server program i can adjust because i need to get a clear idea on what's going around. Thank you

Just switch the while loops between the two programs, making sure to update symbol names as appropriate. If it's easier, switch the bind/listen/accept and connect code between the two. As a third alternative, create 4 functions:

A function to listen to the port.
A function to connect to the port.
A function that writes first, reads second in a loop.
A function that reads first, writes second in a loop.

Put this in a single program and pair choices of 1 or 2 and 3 or 4 depending on whether or not the instance is the client or the server.
Kevin Barry