Block select () on stdin, there won't be a timeout

I am writing a program that receives UDP messages and also receives data from users, however my STDIN still blocks the selection. When I FD_CLR, stdin fd works fine before selecting a program, indicating that the stdin socket is always ready to read data from it. I tried introducing temporary television to time, but this does not seem to work. Should I close the socket somewhere or call FD_CLR, where I am not? The end result should not be a blocking STDIN, but it is currently blocking. Thank you.

int
wait_for_input(){
            fd_set fds;
            int maxfd, sd, err, n;
            struct sockaddr_in addr;
            char stdbuf[BUFLEN];
            unsigned char udpbuf[BUFLEN];

            //memset(stdbuf,0x0,sizeof(stdbuf));
            memset(stdbuf,0x0,sizeof(udpbuf));

            sd = socket(AF_INET, SOCK_DGRAM, 0);

            if(sd<0) {
            printf("Failed to Open UDP socket");
            }

            addr.sin_family = AF_INET;
            addr.sin_addr.s_addr = htonl(INADDR_ANY);
            addr.sin_port = htons(host_list[0]->port);
            err = bind(sd,(struct sockaddr *) &addr,sizeof(addr));

            if(err < 0){
                            printf("ERROR: Cant bind port");

            }

                            struct timeval tv;
            while(1){
                            FD_ZERO(&fds);
                            FD_SET(STDIN_FILENO,&fds);
                            FD_SET(sd,&fds);
                            tv.tv_sec = 1;
                            tv.tv_usec = 0;
                            fflush(stdout);
                            select(sd+1,&fds,NULL,NULL,&tv);

                            // If a UDP message arrives
                            if(FD_ISSET(sd,&fds)){
                                            n = recv(sd,udpbuf,sizeof(udpbuf),0);
                                            unpack(udpbuf);
                                            recompute_my_dv();
                                            fflush(stdout);

                             }
                            //If console data is entered.
                                if(FD_ISSET(STDIN_FILENO, &fds)){
                                            fgets(stdbuf,sizeof(stdbuf),stdin);
                                            parse(stdbuf);
                                            printf("server> ");
                                            fflush(stdout);
                                            FD_CLR(STDIN_FILENO,&fds);


                             }

                     }



 return 0;
 }