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

int main(int argc, char **argv)
{
	int yes=1;
	int pid;
	int udpsock;
	struct sockaddr_in server;
	struct sockaddr_in client;
	int length=sizeof(struct sockaddr_in);

	if(argc!=2)
	{
		fprintf(stdout,"usage: %s <port>\n",argv[0]);
		fflush(stdout);
		return -1;
	}

	if((udpsock=socket(AF_INET,SOCK_DGRAM,0))==-1)
	{
		fprintf(stdout,"error occurred while creating socket %d %s\n",errno,strerror(errno));
		fflush(stdout);
		return -1;
	}

	if(setsockopt(udpsock,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) 
	{
		fprintf(stdout,"error occurred while setting socket option %d %s\n",errno,strerror(errno));
		fflush(stdout);
	}

	server.sin_family=AF_INET;
	server.sin_port=htons(atoi(argv[1]));
	server.sin_addr.s_addr=INADDR_ANY;
	memset(server.sin_zero,0,8);

	if(bind(udpsock,(struct sockaddr *)&server,sizeof(struct sockaddr_in))!=0)
	{
		fprintf(stdout,"failed to bind socket to server address %d %s\n",errno,strerror(errno));
		fflush(stdout);
		return -1;
	}

	if(recvfrom(udpsock,&pid,sizeof(int),0,(struct sockaddr*)&client,(socklen_t*)&length)<0)
	{
		fprintf(stdout,"failed to recv on socket %d %s\n",errno,strerror(errno));
		fflush(stdout);
	}
	else
	{
		fprintf(stdout,"the process id of the client process is %d\n",pid);
		fflush(stdout);
	}
	close(udpsock);
	return 0;
}