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

#define MAX_BUF 1024

int main(int argc, char* argv[])
{
	int sockd;
	struct sockaddr_in my_name, cli_name;
	char buf[MAX_BUF];
	int status;
	int addrlen;

	if (argc < 2)
	{
		fprintf(stderr, "Usage: %s port_number\n", argv[0]);
		exit(1);
	}
	/* create a socket */
	sockd = socket(AF_INET, SOCK_DGRAM, 0);
	if (sockd == -1)
	{
		perror("Socket creation error");
		exit(1);
	}

	/* server address */
	my_name.sin_family = AF_INET;
	my_name.sin_addr.s_addr = INADDR_ANY;
	my_name.sin_port = htons(atoi(argv[1]));

	status = bind(sockd, (struct sockaddr*)&my_name, sizeof(my_name));

	addrlen = sizeof(cli_name);
	status = recvfrom(sockd, buf, MAX_BUF, 0,
			(struct sockaddr*)&cli_name, &addrlen);

	printf("%s", buf);
	strcat(buf, "OK!\n");

	status = sendto(sockd, buf, strlen(buf)+1, 0,
			(struct sockaddr*)&cli_name, sizeof(cli_name));

	close(sockd);
	return 0;
}