asynchronous udp server client application

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C

UDP

sockets

am trying to make an asynchronous udp chat application currently havung only one client and server.the problem is that when I run my server it displays a lot of redundant data and afterward whwn some text is typed displays the error"Error sending the file! \n"... Could someone please look at the code and let me know where am I going wrong???

u_long iMode=1;
       ioctlsocket(sd,FIONBIO,&iMode);
       int n=sd+1;


       fd_set readfds,writefds;
       while(1)
                {
        FD_ZERO(&readfds);
        FD_ZERO(&writefds);
        FD_SET(sd,&readfds);
        FD_SET(sd,&writefds);

       int rv = select(n, &readfds, &writefds, NULL, NULL);
       if(rv==-1)
       {
           printf("Error in Select!!!\n");
           exit(0);
       }
       if(rv==0)
       {
         printf("Timeout occurred\n");
       }
       if (FD_ISSET(sd, &readfds))
       {
           FD_CLR(sd,&readfds);
           int client_length = (int)sizeof(struct sockaddr_in);
           memset(&buffer,0,sizeof(buffer));
          int bytes_received = recvfrom(sd, buffer,SIZE, 0, (struct sockaddr *)&client, &client_length);
      if (bytes_received < 0)
       {
      fprintf(stderr, "Could not receive datagram.\n");
      closesocket(sd);
      WSACleanup();
      exit(0);
       }
       }

  printf("\nClient says: %s",buffer);



  printf("\nWrite :");


  fgets(buffer,SIZE,stdin);

  if(FD_ISSET(sd,&writefds))
      {
          FD_CLR(sd,&writefds);
          int client_length = (int)sizeof(struct sockaddr_in);
          if(sendto(sd, buffer,strlen(buffer), 0, (struct sockaddr *) &client,client_length)<0)
                  {
              printf("Error sending the file! \n");
              exit(1);
                  }
      }


              }
            closesocket(sd);
            WSACleanup();

           return 0;

             }