Well thanks all ,I haved fixed the bug . Actuall the code at the server was a little wrong
Code:
for(i=0;i<5;i++)
{
if(nclient[i]>0&&FD_ISSET(nclient[i],&rset)>0)
{
printf("client[%d] is =%d\n",i,nclient[i]);
read(nclient[i],buf,sizeof(buf));
printf("msg from client[%d]=%s",i,buf);
write(nclient[i],buf,sizeof(buf));
}
}