Network Programing question

[graciano]

Hello
I was curiouse about this subject so i found some useful information at http://beej.us/guide/bgnet/output/html/multipage/index.html .
I found the code for the functions "sender" and "receiver" and made some small changes.
Then i created a program that uses the loopback address that allows me to test the program in two different console windows.
In console 1 the app is executed in receive mode.
In console 2 in send mode.
10 'x' are sent, one per second, but they are only shown when the program ends.
What am i dealing with here? A streaming misusage or a network misusage?
I will post the code below so that anyone interested can give me a hand:)

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <iostream>
#include <string>
#include <netdb.h>
#define MYPORT     4950	// portos de comunicação do emissor e do receptor
#define SERVERPORT 4950	
#define MAXBUFLEN 100	// embora a mensagem possa conter até 100 caracteres, este exemplo apenas troca mensagens de 1 caracter + '\0'
using namespace std;

char ip_emissor[]="127.0.0.1";	//endereço ip do host que vai funcionar como emissor
char ip_receptor[]="127.0.0.1";	//endereço ip do host que vai funcionar como receptor


char receiver(){
	int sockfd;
	struct sockaddr_in my_addr;	// endereço ip do receptor(obtido pela aplicação do host onde é executada) 
	struct sockaddr_in their_addr;  // endereço ip do emissor(obtido pela aplicação do host onde é executada)
	socklen_t addr_len;
	int numbytes;
	char buf[MAXBUFLEN];
	if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
		perror("socket");
		exit(1);
	}

	my_addr.sin_family = AF_INET;		 // host byte order
	my_addr.sin_port = htons(MYPORT);	 // short, network byte order
	my_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP
	memset(my_addr.sin_zero, '\0', sizeof my_addr.sin_zero);

	if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof my_addr) == -1) {
		perror("bind");
		exit(1);
	}

	addr_len = sizeof their_addr;
	if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0,
		(struct sockaddr *)&their_addr, &addr_len)) == -1) {
		perror("recvfrom");
		exit(1);
	}

	//cout << "Pacote recebido de "<< inet_ntoa(their_addr.sin_addr) << endl; 		
	buf[numbytes] = '\0';
	//cout << buf << endl;
	close(sockfd);
	
	//Return list:
	//'0' se o pacote não é proveniente do ip_emissor
	//cout<<"ip do emissor actual  : "<<inet_ntoa(their_addr.sin_addr)<<endl;
	//cout<<"ip do emissor esperado: "<<ip_emissor<<endl;
	if(strcmp(inet_ntoa(their_addr.sin_addr),ip_emissor)!=0){
		cout<<"Pacote ignorado\n";return '0';
	}else	return buf[0];

	
}
void sender(char c){
	int sockfd;
	struct sockaddr_in their_addr; // connector's address information
	struct hostent *he;
	int numbytes;
	char caracter[2]={c, '\0'};

	if ((he=gethostbyname(ip_receptor)) == NULL) {  // get the host info
		perror("gethostbyname");
		exit(1);
	}

	if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
		perror("socket");
		exit(1);
	}

	their_addr.sin_family = AF_INET;	 // host byte order
	their_addr.sin_port = htons(SERVERPORT); // short, network byte order
	their_addr.sin_addr = *((struct in_addr *)he->h_addr);
	memset(their_addr.sin_zero, '\0', sizeof their_addr.sin_zero);

	if ((numbytes = sendto(sockfd, caracter, strlen(caracter), 0,
			 (struct sockaddr *)&their_addr, sizeof their_addr)) == -1) {
		perror("sendto");
		exit(1);
	}

	printf("sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));
	close(sockfd);
}


int main(){
	char mode;
	int i,numberofchar=10;
	cout<<"(s) to send; (r) to receive.\nEnter mode: ";cin>>mode;
	if(mode=='s'){
			cout<<"Send mode ...\n";
			for(i=0;i<numberofchar;i++){
					sender('x');
					sleep(1);
			};
	}
	else{   
			cout<<"Receive mode ...\n";
			for(i=0;i<numberofchar;i++){
					cout<<receiver();
			};
			cout<<endl;
	}
	return 0;
}

Thanks

[Zaita]

line 113.

cout<<receiver();
cout.flush();

:) That should clear the cout buffer and render to the screen.

[graciano]

Thanks ... that is what i needed.
I tried cin.ignore() and as it didn't work i got confused.