udp.c

/*
 * udp.c: This class listens/creates a UDP socket to accept JOIN request
 * This file is a part of Tutor
 *
 * Tutor is an application to create a tutor relationship tree using the client-server model.
 * Consists of a tutor node (server) and many student nodes (clients).
 * This was created as a part of CS 6390 Advanced Computer Networks course at UT Dallas.
 *
 * Contributors: Avinash Joshi <axj107420@utdallas.edu>, Sandeep Shenoy <sxs115220@utdallas.edu>
 */

#include "myheader.h"

int child_count=0;
int k_child=0;
int tcpport=0;

// Functin definition
static void* handle_udp(void*);

/*
 * The node_details holds the structure for the list of 
 * nodes a.k.a 'children' to be sent if join is not accepted
 */
struct node_details {
	int		nid;
	char	node_ip[30];
	int		node_udpport;
	int		nchildren;
} node_det[10];

/*
 * This function creates a new thread for the UDP socket
 *
 */
void
create_udp (size_t uport,size_t tport,int k) {
	k_child = k;
	tcpport = tport;

	pthread_t udp_pid;

	pthread_create(&udp_pid,NULL,&handle_udp,(void *)uport);
	return;
}

/*
 * This function opens and binds the UDP socket at the requested port
 *
 */
static void*
handle_udp (void* uport) {

	pthread_detach(pthread_self());
	int udp_sockfd, bytes_received, bytes_sent, client_addr_size;
	struct sockaddr_in server_addr, client_addr;
	char udp_buffer[STRLEN];
	char udp_list_buffer[STRLEN];
	char temp_k[20];
	char server_host[50];
	struct hostent *he;
	int m = 0;

	//Creates a UDP socket
	if ((udp_sockfd = socket (AF_INET,SOCK_DGRAM,0)) < 0) {
		perror ("socket() failed");
		return NULL;
	}

	//Creates a local server structure
	bzero (&server_addr,sizeof(server_addr));
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons ((size_t)uport);
	server_addr.sin_addr.s_addr = htonl(INADDR_ANY);

	bzero (&udp_list_buffer,sizeof(udp_list_buffer));

	gethostname (server_host, 49);
	if ((he = gethostbyname(server_host)) == NULL) {
		herror(server_host);
		fprintf (stdout, "Unable to resolve host %s", server_host);
		exit (EXIT_FAILURE);
	}
	struct in_addr **tmp = (struct in_addr **) he->h_addr_list;
	DBG (("Hostname:IP = %s:%s", server_host, inet_ntoa(*tmp[0])));

	/*Binds the socket*/
	if (bind (udp_sockfd, (struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
		perror ("bind() failed");
		exit (EXIT_FAILURE);
	}
	int next_node = (node_number * k_child) + 1;

	DBG (("%s \n","UDP Socket created"));

	/*Blocking Receive call that keeps waiting for join request*/
	client_addr_size = sizeof(client_addr); 
	while (1)
	{
		bzero (&udp_buffer,sizeof(udp_buffer));
		char temp[STRLEN];
		if ((bytes_received = recvfrom(udp_sockfd, udp_buffer, STRLEN, 0, (struct sockaddr *) &client_addr, (socklen_t *) &client_addr_size)) < 0) {
			perror ("recvfrom() failed");
			exit (EXIT_FAILURE);
		}

		char temp_buff[50], *temp_port, *temp_command;
		int child_port;
		strcpy(temp_buff,udp_buffer);

		temp_command = strtok (temp_buff, ":");
		temp_port = strtok (NULL, ":");
		child_port = atoi(temp_port);

		if (strcmp( temp_command , "join") == 0) {
			if (child_count < k_child ) {
				strcpy(temp,"accept:");
				sprintf(temp_k,"%s", inet_ntoa(*tmp[0]));
				strcat(temp,temp_k);
				node_det[child_count].nid = node_number;
				strcpy(node_det[child_count].node_ip,inet_ntoa(client_addr.sin_addr));
				strcat(temp,":");
				sprintf(temp_k,"%d",tcpport);
				node_det[child_count].node_udpport = child_port;
				strcat(temp, temp_k);
				strcat(temp,":");
				sprintf(temp_k,"%d",k_child);
				node_det[child_count].nchildren = k_child;
				strcat(temp, temp_k);
				strcat(temp,":");
				sprintf(temp_k,"%d",next_node);
				strcat(temp, temp_k);
				strcat(temp,"\0");
				next_node++;
				DBG (("Sending %s", temp));
				if ((bytes_sent = sendto(udp_sockfd,temp,strlen(temp),0,(struct sockaddr *)&client_addr,client_addr_size)) < 0) {
					perror ("sendto() failed");
					exit (EXIT_FAILURE);
				}
				child_count++;
			}
			else {	
				char temp_b[30];
				bzero (temp, sizeof(temp));
				for (m=0;m<k_child;m++) {
					sprintf(temp_b,"%d",node_det[m].nid);
					strcat(temp,temp_b);
					strcat(temp,":");
					strcat(temp,node_det[m].node_ip);
					strcat(temp,":");
					sprintf(temp_b,"%d",node_det[m].node_udpport);
					strcat(temp,temp_b);
					strcat(temp,":");
					sprintf(temp_b,"%d",node_det[m].nchildren);
					strcat(temp,temp_b);
					if(m != k_child-1)
						strcat(temp,",");	
				}
				DBG (("Sending %s",temp));
				if ((bytes_sent = sendto(udp_sockfd,temp,strlen(temp),0,(struct sockaddr *)&client_addr,client_addr_size)) < 0) {
					perror ("sendto() failed");
					exit (EXIT_FAILURE);
				}
			}
		}

	}
	return NULL;
}