#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

void error(char *msg)
{
    perror(msg);
    exit(0);
}

int main(int argc, char *argv[])
{
    int sockfd, portno, n, i, nof_tx_char;
    int sockfd_conf, portno_conf;
    struct sockaddr_in serv_addr;
    struct sockaddr_in conf_addr;
    struct hostent *server;

    unsigned short int  buffer[256];
    char disp[15];
    char hostname[30];
    const char default_hostname[] = "GAA0113931.fritz.box";

    if (argc !=  2) {
     if (argc == 1)
     {
       // if no hostname is given use default
       strcpy(hostname,default_hostname);
     }
      else
     {
       fprintf(stderr,"usage %s hostname \n", argv[0]);
       exit(0);
     }
    }
    else
    {
      strcpy(hostname,argv[1]);
    }
    // socket to transfer data
    portno = 1000;
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0)
        error("ERROR opening socket");

    server = gethostbyname(hostname);
    if (server == NULL) {
        fprintf(stderr,"ERROR, no such host\n");
        exit(0);
    }

    // socket addr for config socket
    bzero((char *) &conf_addr, sizeof(struct sockaddr_in));
    conf_addr.sin_family = AF_INET;
    bcopy((char *)server->h_addr,
         (char *)&conf_addr.sin_addr.s_addr,
         server->h_length);
    conf_addr.sin_port = htons(portno_conf);
    // socket addr for data socket
    bzero((char *) &serv_addr, sizeof(struct sockaddr_in));
    serv_addr.sin_family = AF_INET;
    bcopy((char *)server->h_addr,
         (char *)&serv_addr.sin_addr.s_addr,
         server->h_length);
    serv_addr.sin_port = htons(portno);

    if (connect(sockfd,(struct sockaddr*)&serv_addr,sizeof(struct sockaddr_in)) < 0)
        error("ERROR connecting");

    bzero(buffer,256);

    buffer[0]='5'; 
    buffer[1]='2'; 
    buffer[2]='0';

    buffer[3]=0xff;
    buffer[4]=3;
    buffer[5]='1';

    nof_tx_char=6;

    printf ("EUG: Data to be transmitted: ");
    for (i=0;i <  nof_tx_char;i++)
    {
      printf("0x%02x ",buffer[i]);
    }
    printf ("\n");

    n = write(sockfd,buffer,nof_tx_char);
    printf("EUG: Data - #Bytes transmitted:  %d\n", n);
    if (n < 0)
         error("ERROR writing to socket");
    close(sockfd);
    return 0;

}

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

void error(char *msg)
{
    perror(msg);
    exit(1);
}

int main(int argc, char *argv[])
{
     int conf_sockfd, data_sockfd, newsockfd, conf_portno, data_portno,clilen;
     char buffer[256];
     struct sockaddr_in serv_addr, cli_addr;
     int i,n;
     data_sockfd = socket(AF_INET, SOCK_STREAM, 0);
     if (data_sockfd < 0)
        error("ERROR opening socket");

     bzero((char *) &serv_addr, sizeof(serv_addr));
     conf_portno = 1001;
     data_portno = 1000;
     serv_addr.sin_family = AF_INET;
     serv_addr.sin_addr.s_addr = INADDR_ANY;
     serv_addr.sin_port = htons(data_portno);
     if (bind(data_sockfd, (struct sockaddr *) &serv_addr,
              sizeof(serv_addr)) < 0)
              error("ERROR on binding");
     listen(data_sockfd,5);
     clilen = sizeof(cli_addr);
     newsockfd = accept(data_sockfd,
                 (struct sockaddr *) &cli_addr,
                 &clilen);
     if (newsockfd < 0)
          error("ERROR on accept");
     bzero(buffer,256);
     n = read(newsockfd,buffer,255);
     if (n < 0) error("ERROR reading from socket");
     printf("%s: Here is the message: '%s'\n",argv[0],buffer);
     printf("%s: ",argv[0]);
     for (i=0; i < 2*n; i++)
      printf("0x%02x ",buffer[i]);
     printf("\n");
     printf("%s: #Bytes received: %d\n",argv[0],n);
     return 0;
}