Linux Server TCP/IP 2

#include<stdio.h>
#include<stdlib.h>
#include<string.h>    //strlen
#include<sys/socket.h>
#include<arpa/inet.h> //inet_addr
#include<unistd.h>    //write
#include<stddef.h>
int main(int argc, char *argv[])
{
    int socket_desc, new_sd, c, sd;
    struct sockaddr_in server, client;
    char *message;

    //Create socket
    socket_desc = socket(AF_INET, SOCK_STREAM, 0);
    if (socket_desc == -1)
    {
        puts("Could not create fsocket");
    }

    //Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(8888);

    //Bind
    if (bind(socket_desc, (struct sockaddr *)&server, sizeof(server)) < 0)
    {
        puts("bind failed");
        return 1;
    }
    puts("bind done");

    //Listen
    listen(socket_desc, 3);

    //Accept and incoming connection
    puts("Waiting for incoming connections...");
    c = sizeof(struct sockaddr_in);
    const int RECV_BUF_SIZE = 512;
    char recv_buf[RECV_BUF_SIZE];
    int n, nwrote;

    while (1)
    {
        // try to accept socket
        new_sd = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c);

        // > 0 - real socket, 0==localhost
        if (new_sd >= 0) {

            puts("Connection accepted\r\n");

            int i = 0;
            int fnd = 0; // terminating character found
            int tread = 0; // total bytes read

            // receive loop
            do {
                // read a max possible bytes from buffer
                if ((n = read(new_sd, &recv_buf[tread], RECV_BUF_SIZE - tread)) < 0) {
                    puts("error reading from socket, closing socket\r\n");
                    break;
                }

                // succesfull read
                if (n > 0)
                {
                    printf("%d rcvd\r\n", n);
                    tread += n;
                    // should never happen
                    if (tread >= RECV_BUF_SIZE) {
                        // flag as error
                        fnd = 2;
                        break;
                    }
                }

                // break after end of the message
                for (i = 0; i < tread; i++) {
                    // test for terminatign character
                    if (recv_buf[i] == 0)
                    {
                        puts("0 found\r\n");
                        fnd = 1;
                    }
                }

            } while (!fnd);

            // we may write anywhere, but this one control the ACT LED
            FILE *fp = fopen("/sys/class/leds/led0/brightness", "w");
            if (fp != NULL) {
                fwrite(recv_buf, 1, strlen(recv_buf), fp);
                fclose(fp);
            } else {
                printf("error opening LED0\r\n");
            }

            // read temperature
            float temp;
            fp = fopen("/sys/class/thermal/thermal_zone0/temp", "r");
            if (fp != NULL) {
                fscanf(fp, "%f", &temp);
                temp /= 1000;
                fclose(fp);
            }

            // close connection if buffer overrunned
            if (fnd > 1) {
                printf("an error occured\r\n");
                close(new_sd);
                break;
            }

            printf("sending response %f\r\n", temp);

            int twrote = 0; // total bytes written
            int sent = 0;   // sent completition flag
            char snd_buf[RECV_BUF_SIZE]; // will send from this buf
            // print temperature to recv buf
            sprintf(snd_buf, "%f", temp);
            // reply to client loop, see rcv loop for better understanding
            do {
                n = write(new_sd, &snd_buf[twrote], strlen(snd_buf) - twrote + 1 );
                if (n < 0) {
                    puts("ERROR responding to client echo request\r\n");
                    puts("Closing socket\r\n");
                    close(new_sd);
                    break;
                }
                if (n > 0) {
                    twrote += n;
                    if (twrote == strlen(snd_buf) +1 ) {
                        sent = 1;
                    }
                }
            } while (!sent);

            printf("OK sent %d\r\n", twrote);
            // we are done, wait for new connection ...
            close(new_sd);
        }
    }
    return 0;
}