.c

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

typedef struct UDP_message_t
{
	int ip;
	int portNumber;
	char* message;
	int messageLength;
} UDP_message_t;

int listenForMessage (W int portNo, char* receiveBuffer, UDP_message_t* udpMessage, int maxBufferSize )
{
	struct sockaddr_in listenSocket, receiveSocket;
	//int ipAddressLengthInBytes = 16;
	
	int s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if ( s == -1 )
	{
		printf("Failed to create UDP server");
		return -1;
	}
	
	memset( &listenSocket, 0, sizeof(struct sockaddr_in) );
	
	listenSocket.sin_family = AF_INET;
	listenSocket.sin_port = htons(portNo);
	listenSocket.sin_addr.s_addr = htonl(INADDR_ANY);
	
	bool successfulBind = bind( s, (struct sockaddr*)&listenSocket, sizeof(struct sockaddr_in) ) != -1 ? true : false;
	if (!successfulBind)
	{
		printf("failed to bind");
		return -1;
	}
	
	while(1)
	{
		printf("waiting for data \n");
		fflush(stdout);
		
		
		int receiveLength;
		int slen = 16;
		receiveLength = recvfrom(s, receiveBuffer, 1024, 0, (struct sockaddr*) &receiveSocket, &slen);
		
		if ( receiveLength == -1 )
		{
			printf("failed to receive message");
			return -1;
		}
		else
		{
			printf("\nReceived data: ");
			int i;
			
			for ( i = 0; i < receiveLength; i++)
			{
				printf("%c", receiveBuffer[i]);
			}
			printf("\n");
			
			
			printf("\n\n sender is %d:%d\n", receiveSocket.sin_addr.s_addr, receiveSocket.sin_port);
			
		}
		close(s);
		
		udpMessage->ip = ntohl(receiveSocket.sin_addr.s_addr);
		udpMessage->portNumber = ntohs(receiveSocket.sin_port);
		udpMessage->message = receiveBuffer;
		udpMessage->messageLength = receiveLength;
		
		return receiveLength;
		
	}
	
	
}

int main(int argc, char **argv)
{
	
	int portNumber = atoi(argv[1]);
	char message[1024];
	UDP_message_t* udpMsg;
	int numBytesReturned = listenForMessage( portNumber, message, udpMsg, 1024 );
	
	printf("\n\number of bytes returned %d", numBytesReturned); 
	
    return 0;
    
    
}