UDP echo client-server implementation

client.c

#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

int main() {
	const char* server_name = "localhost";
	const int server_port = 8877;

	struct sockaddr_in server_address;
	memset(&server_address, 0, sizeof(server_address));
	server_address.sin_family = AF_INET;

	// creates binary representation of server name
	// and stores it as sin_addr
	// http://beej.us/guide/bgnet/output/html/multipage/inet_ntopman.html
	inet_pton(AF_INET, server_name, &server_address.sin_addr);

	// htons: port in network order format
	server_address.sin_port = htons(server_port);

	// open socket
	int sock;
	if ((sock = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
		printf("could not create socket\n");
		return 1;
	}

	// data that will be sent to the server
	const char* data_to_send = "Gangadhar Hi Shaktimaan hai";

	// send data
	int len =
	    sendto(sock, data_to_send, strlen(data_to_send), 0,
	           (struct sockaddr*)&server_address, sizeof(server_address));

	// received echoed data back
	char buffer[100];
	recvfrom(sock, buffer, len, 0, NULL, NULL);

	buffer[len] = '\0';
	printf("recieved: '%s'\n", buffer);

	// close the socket
	close(sock);
	return 0;
}

server.c

#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[]) {
	// port to start the server on
	int SERVER_PORT = 8877;

	// socket address used for the server
	struct sockaddr_in server_address;
	memset(&server_address, 0, sizeof(server_address));
	server_address.sin_family = AF_INET;

	// htons: host to network short: transforms a value in host byte
	// ordering format to a short value in network byte ordering format
	server_address.sin_port = htons(SERVER_PORT);

	// htons: host to network long: same as htons but to long
	server_address.sin_addr.s_addr = htonl(INADDR_ANY);

	// create a UDP socket, creation returns -1 on failure
	int sock;
	if ((sock = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
		printf("could not create socket\n");
		return 1;
	}

	// bind it to listen to the incoming connections on the created server
	// address, will return -1 on error
	if ((bind(sock, (struct sockaddr *)&server_address,
	          sizeof(server_address))) < 0) {
		printf("could not bind socket\n");
		return 1;
	}

	// socket address used to store client address
	struct sockaddr_in client_address;
	int client_address_len = 0;

	// run indefinitely
	while (true) {
		char buffer[500];

		// read content into buffer from an incoming client
		int len = recvfrom(sock, buffer, sizeof(buffer), 0,
		                   (struct sockaddr *)&client_address,
		                   &client_address_len);

		// inet_ntoa prints user friendly representation of the
		// ip address
		buffer[len] = '\0';
		printf("received: '%s' from client %s\n", buffer,
		       inet_ntoa(client_address.sin_addr));

		// send same content back to the client ("echo")
		sendto(sock, buffer, len, 0, (struct sockaddr *)&client_address,
		       sizeof(client_address));
	}

	return 0;
}