/* This program creates a datagram server process 
   in the internet domain.  it listens on port
   51717.   On solaris, compile like this
   gcc -g -Wall server.udp.c -lnsl -lsocket */
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<netdb.h>
#include<stdio.h>
#include<strings.h>
#include<arpa/inet.h> 
#define BUFSIZE 1024

void error(char *);
int main()
{
   int sock, length, fromlen, n;
   struct sockaddr_in server;
   struct sockaddr_in from;
   char buf[BUFSIZE];

   sock=socket(AF_INET, SOCK_DGRAM, 0);
   if (sock < 0)
       error("Opening socket");
   length = sizeof(server);
   bzero(&server,length);
   server.sin_family=AF_INET;
   server.sin_addr.s_addr=INADDR_ANY;
   server.sin_port=htons((unsigned short)51717);
   if (bind(sock,(struct sockaddr *)&server,length)<0) 
       error("binding"); 
   while (1) {
       n = recvfrom(sock,buf,BUFSIZE,0,(struct sockaddr *)&from,&fromlen);
       if (n < 0) error("recvfrom");
       buf[n]='\0';
       printf("The message from %s is %s\n",
            inet_ntoa((struct in_addr)from.sin_addr), buf);
       n = sendto(sock,"Got your message",16,0,(struct sockaddr *)&from,fromlen);
       if (n < 0) error("sendto");
   }
   return 0;
 }

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