socket programming

hi
i 'm new to socket programming trying to write a server which sends message(by getting a string using fgets in a while loop ) to clients its sends the first messge but didnot send the next message also it shows bind error if i run it again from the same terminal
client connects using telnet
please help

Code:

#include<unistd.h>
int main()
{  int sock,new;
   struct sockaddr_in server,client;
   int len=sizeof(struct sockaddr);
   char msg[50]="first tcp sockets programme\n";
   if ((sock=socket(AF_INET,SOCK_STREAM,0))==-1)
      { perror("socket:");
        exit(-1);
      }
   //now bind the server port
   server.sin_family=AF_INET;
   server.sin_port  =htons(9000);
   server.sin_addr.s_addr=INADDR_ANY;
   bzero(&server.sin_zero, 8);
   if ((bind(sock,(struct sockaddr *)&server,sizeof(struct sockaddr) ))==-1)
      {perror("bind error:");
       exit(-1);
      }
  listen(sock,2);
  // listen seldom  gines error
  while(1)
     {if((new=accept(sock,(struct sockaddr *)&client,&len))==-1)
     {perror("accept:");
      exit(-1);
     }
  //sending message     
     fgets(msg ,20,stdin);
send(new,msg,strlen(msg),0);
     }
 close(new);//describe the client socket 
 close(sock);
}

35,6 63%

Oh you forgot code? You may as well of left it out because no one is going to be able to help you unless you learn to stylize your code and use the forums code tags. The object of programming isn't to use the least amount of lines as possible so don't do this:

Code:

while(1)
{if((new=accept(sock,(struct sockaddr *)&client,&len))==-1)
{perror("accept:");
exit(-1);
}

Code:

#include<unistd.h>
#include <WinSock2.h>
int main()
{  int sock,new;
   struct sockaddr_in server,client;
   int len=sizeof(struct sockaddr);
   char msg[]="first tcp sockets programme\n";
   if (sock=socket(AF_INET,SOCK_STREAM,0))
      { perror("socket:");
        exit(-1);
      }
   //now bind the server port
   server.sin_family=AF_INET;
   server.sin_port  =htons(9000);
   server.sin_addr.s_addr=INADDR_ANY;
   bzero(&server.sin_zero, 8);
   if (bind(sock,(struct sockaddr *)&server,sizeof(struct sockaddr) ))
      {perror("bind error:");
       exit(-1);
      }
  listen(sock,2);
  // listen seldom  gines error
  while(1)
     {if(new=accept(sock,(struct sockaddr *)&client,&len))
     {perror("accept:");
      exit(-1);
     }
  //sending message     
     fgets(msg ,20,stdin);
send(new,msg,strlen(msg),0);
     }
 closesocket(new);//describe the client socket 
 closesocket(sock);
}

as for the formatting, pick one style and stick with it, it doesnt really matter too much how you format, but mixing styles makes your code look sloppy.

Code:

   if(condition)
      { statement();
      }

is very unusual, although syntactically correct.

Originally Posted by sunil

Code:

  while(1)
     {if((new=accept(sock,(struct sockaddr *)&client,&len))==-1)
     {perror("accept:");
      exit(-1);
     }
  //sending message     
     fgets(msg ,20,stdin);
send(new,msg,strlen(msg),0);
     }
 close(new);//describe the client socket

close(new); has to be in the while loop, otherwise new will be assigned a new socket, but the old one will not be closed, thus creating more and more sockets.
this is also the problem why a client is just sent one message. what your code does is:
1. assign new the socket of the first client
2. get a message from stdin
3. send that message via new
4. assign new the next client

Obviously, this can not work. You should either close new in the loop (this way, the clients need to reconnect after every sent message), or use threads/fork() to keep each client connection alive.

The bind error is absolutely fine. It's because after closing a socket it still hangs around until the kernel clears it. While that socket is still around and you run the programm again.. you can't bind to that address because it's already bound. setsockopt() it the call you need to prevent this. Just set SO_REUSEADDR on that socket.