[Question] tcp client and server connection problems

silentkill89 · 09-01-2011, 04:11 AM

As the topic, I want to be clear on how to connect between pc which 1 pc is running as server and another as client.
Im still a newbie in Linux networking so forgive me if im wrong.
Below is my code:

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;
}

and client

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;
}

My code can only run in same pc, which means between terminal, but when running on another pc, it does not display anything but server side keep waiting for client respond and it stil not displaying anything after few hours later. I know i need to add some code like listen(), but I'm still not clear on how to do it. Thousand appreciate.

silentkill89 · 09-01-2011, 05:41 AM

can anyone please help me out? I'm urgently need to know the solution

any guidance or example will do help me. Thanks

chrism01 · 09-01-2011, 08:53 PM

Well, its been a while since I did sockets, & that was in Perl, but the principles are the same.
It looks to me (in client code) that the server_addr is derived from 'host = gethostbyname("127.0.0.1");' which is localhost interface. I think you need to specify actual remote server addr.
Have you read this http://beej.us/guide/bgnet/ ?

silentkill89 · 09-03-2011, 01:03 PM

do i have to buy the book? if so i rather search for some online tips

by the way chris, does that problem you mentioned above conflict with ip address too? because when i try to enter the ip, it still nothing happen, just like keep waiting and no response from client. Can you provide me some tips to that? Sorry im still in learning. Thank you

chrism01 · 09-04-2011, 07:04 PM

If you looked at the link, you'd see

Quote:

HTML:

One section per page (read online)
All on one page (read online)

One section per page (tarball for download)
One section per page (zipfile for download)
All on one page (tarball for download)
All on one page (zipfile for download)

PDF:

US Letter, one sided
US Letter, two sided
A4, one sided
A4, two sided

You might also want to use the Report button to ask the Mods to move this to the Programming forum for quicker/better answers

dwhitney67 · 09-04-2011, 08:27 PM

The call to connect() has an error (see text in bold font):

Code:

if (connect(sock, (struct sockaddr *)&server_addr,
            sizeof(struct sockaddr)) == -1)

Replace the bold-font text with "sockaddr_in".

A few other comments: gethostbyname() and bzero() are deprecated functions; gets() is unsafe to use. Use getaddrinfo(), memset(), and fgets() instead.

And here, you take the risk of a buffer overflow:

Code:

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

recv_data[bytes_recieved] = '\0';   <--- if 1024 bytes are received, this will cause a
                                                buffer overflow (index should be in range of 0-1023.

P.S. And it is 'i' before 'e', except when followed by 'c'; thus the correct spelling is "received".

crabboy · 09-04-2011, 08:27 PM

Same question in two separate threads. Follow the discussion in the other thread, this one is being closed.

http://www.linuxquestions.org/questi...5/#post4461226