/*********************************************************************************
 *      Copyright:  (C) 2018 LingYun IoT Studio
 *                  All rights reserved.
 *
 *       Filename:  udp_server.c
 *    Description:  This file is UDP socket server sample source code, it will 
 *                  echo back the receive data from client.
 *                 
 *        Version:  1.0.0(10/23/2018)
 *         Author:  Guo Wenxue <guowenxue@gmail.com>
 *      ChangeLog:  1, Release initial version on "2017-10-23 01:41:05 PM"
 *                 
 ********************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define DEF_SERV_PORT 8059

void dump_buf(char *buf, int size)
{
    int  i;

    for(i=0; i<size; i++)
    {
        printf("0x%02x ", buf[i]);
    }

    printf("\n");
}

int main(int argc, char **argv)
{
    struct sockaddr_in      servaddr, cliaddr;
    socklen_t               cliaddr_len;
    int                     sockfd;
    char                    buf[1024];
    char                    ip[INET_ADDRSTRLEN];
    int                     i, len;
    int                     port = DEF_SERV_PORT;

    printf("You can use '%s [port]' to change default port[%d].\n", argv[0], DEF_SERV_PORT);

    if( argc == 2 )
    {
        port = atoi(argv[1]);
    }

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(port);

    printf("Start listen on port[%d]\n", port);

    bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr));
    printf("Start Accepting connections ...\n");

    while(1)
    {
        cliaddr_len = sizeof(cliaddr);

        memset(buf, 0, sizeof(buf));
        len = recvfrom(sockfd, buf, sizeof(buf), 0, (struct sockaddr*)&cliaddr, &cliaddr_len);
        if(len == -1)
        {
            printf("recvfrom error: %s\n", strerror(errno));
        }
        printf("Received %d bytes datas from %s at PORT %d\n", len, inet_ntop(AF_INET, &cliaddr.sin_addr, ip, sizeof(ip)), 
                ntohs(cliaddr.sin_port));

        printf("%s\n", buf);
        dump_buf(buf, len);

#if 0
        for(i = 0; i < len; i++)
        {
            buf[i] = toupper(buf[i]);
        }
        dump_buf(buf, len);
#endif

        len = sendto(sockfd, buf, len, 0, (struct sockaddr*)&cliaddr, sizeof(cliaddr));
        if(len == -1)
        {
            printf("sendto error: %s\n", strerror(errno));
        }
    }

    close(sockfd);
    return 0;
}