client.c

#include "MyHeader.h"

// Function that returns the ip of the client.
char  *udp_server_ip() {

	int fd;
	struct ifreq ifr;
	fd = socket(AF_INET,SOCK_DGRAM,0);

	// Defining that the wanted ip is an IPv4 address.
	ifr.ifr_addr.sa_family = AF_INET;

	// IP address attached to "eth0"
	strncpy(ifr.ifr_name, "eth0",IFNAMSIZ-1);
	ioctl(fd,SIOCGIFADDR, &ifr);
	close(fd);

	return inet_ntoa(((struct sockaddr_in *) &ifr.ifr_addr)->sin_addr);
}

int main (int argc, char *argv[]) {

	int sockfd,listenfd,sockudpserv;
	socklen_t udp_clilen;
	short conf;
	struct sockaddr_in servaddr,udp_servaddr,udp_cli_addr;
	char message[512];
	data inf;

	// Checking the number of the arguments
	if (argc<4){
		printf("Error: Not enough arguments\n");
		exit(1);
	}

	// Checking if the first argument is valid.
	if (argv[1][0]!='-' || argv[1][1]!='s') {
		printf("Error: Missing argument -s\n");
		exit(1);
	}

	inf.ip=argv[2];  // Storing argument 2, which is the IP address, into variable ip of struct inf.
	inf.tcp_port=atoi(argv[3]); // Same for argument3, which is tcp port.
	inf.udp_port=atoi(argv[4]); // Same for argument4, which is udp port.

	// Checking if the tcp port is valid.
	if (inf.tcp_port<10770 || inf.tcp_port>10779) {
		printf("Error: invalid tcp port number. Tcp port must be between 10770 and 10779\n");
		exit(1);
	}

	// Checking if the udp port is valid.
	if (inf.udp_port<10770 || inf.udp_port>10779) {
		printf("Error: invalid udp port. Udp port must be between 10770 and 10779\n");
		exit(1);
	}

	//udp port should be different from tcp port.
	if (inf.udp_port==inf.tcp_port) {
		printf("Error: invalid udp_port. Udp port must be different from tcp_port\n");
		exit(1);
	}

	//Create the socket for the client.
	sockfd = socket(AF_INET,SOCK_STREAM,0);
	//Define the characteristics of connection with server.
	bzero (&servaddr,sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port=htons(inf.tcp_port);
	servaddr.sin_addr.s_addr=inet_addr(inf.ip);

	//Connecting with the server and checking at the same time.
	if(connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr))==0) {
		printf("Client was successfully connected to server\n");
		inf.ip=udp_server_ip(); //Storing the ip of client into variable ip of struct inf.
		printf("My ip is: %s\n",inf.ip);
		//Sending information about the client to server.
		write(sockfd,&inf,sizeof(inf));
	}else printf ("There is no server to connect\n");

	// Receiving edited information from server.
	read(sockfd,&inf,sizeof(data));

	//Finding out who is the udp server and printing information.
	if (inf.udp_server==1){
		printf("\nI am the udp server\n");
		printf("\nUdp port: %d\n",inf.udp_port);
		//ending the connection with server.
		close(sockfd);
		//Initializing the udp server as done in server.c document.
		listenfd=socket(AF_INET,SOCK_STREAM,IPPROTO_IP);
		bzero(&udp_servaddr,sizeof(udp_servaddr));
		udp_servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
		udp_servaddr.sin_family=AF_INET;
		udp_servaddr.sin_port=htons(inf.udp_port);
		bind(listenfd,(struct sockaddr*) &udp_servaddr,sizeof(udp_servaddr));
		listen(listenfd,1);

		//Calculating the size of udp client's address for use in accept.
		udp_clilen=sizeof(udp_cli_addr);
		//Connection with the udp client.
		sockudpserv=accept(listenfd,(struct sockaddr*) &udp_cli_addr,&udp_clilen);
		//Checking if the connection is succesfull.
		if (sockudpserv<0) printf("Error: Could not connect with udp client\n");
		else {
			printf("\nSuccessfully connected with udp client\n");
	
			//Receiving messages from udp client until udp client types "exit".
			do {
				read(sockudpserv,&message,sizeof(message));
				printf("%s\n",message);
			} while (strcmp(message,"exit")!=0);
		

		}
	//Knowing who is udp server, the other one is udp client.
	}else if (inf.udp_server==0){
		//Printing information for udp client.
		printf("I am the udp client\n");
		printf("\nServer's ip: %s\n",inf.ip);
		printf("\nUdp port: %d\n",inf.udp_port);
		//Ending connection with server.
		close(sockfd);
	
		//Waiting for 2seconds for the udp server to be initialized.
		sleep(2);	

		//Create socket for udp client
		sockfd = socket(AF_INET,SOCK_STREAM,0);
		//Defining characteristics about the connection with udp server.
		bzero(&servaddr,sizeof(servaddr));
		servaddr.sin_family = AF_INET;
		servaddr.sin_port=htons(inf.udp_port);
		servaddr.sin_addr.s_addr=inet_addr(inf.ip);

		//Checking if the connection is succesfull.
		if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr))==0) {
			printf("\nUdp Client was succefully connected to udp server\n");
	
			//Reading messages from keyboard and sending them to udp server.
			do {
				printf("> ");
				scanf("%s",message);
				write(sockfd, &message, sizeof(message));
			} while (strcmp(message,"exit")!=0);	
		
		}else printf("\nThere is no server to connect\n");


	}else {
		//The case that variable udp_port has negative value.
		printf("Error:Connection can not be accomplished. Different udp ports\n");
		printf("Udp port: %d\n",inf.udp_port);
	}

}