Hallo alle, ich bin ein Neuling in der UNIX / Linux-Socket-Programmierung. Dies ist ein Klasse-Projekt, dass ich Probleme mit.

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Ich habe versucht, "Keep-Alive"-HTTP-Verbindungen auf den Server in einer kleinen Web-Crawler-Projekt. Hier ist das Problem: Ich habe versucht, recv () die erste Seite, es gelang. Jedoch die 2. Folge recv () erhalten Null Bytes, für die ich wirklich keine Ahnung haben. Ich habe ein "Keep-Alive"-Feld in der Anfrage-Nachricht senden, als ich ().

Ich weiss nicht recht wissen, wie die Umsetzung persistente HTTP-Verbindung mit Keep-Alive. Ich extrahiert die Socket-Verbindung Code in ein kleines Programm, wie beigefügt.

Würden Sie bitte einen Blick auf den Code ein, und erklären, was falsch war mit mir? Das wäre eine große Hilfe, da ich sie sich auf die dieses Problem für Tage.

Durch die Art und Weise, das Programm wurde unter SunOS mit g + + und-lsocket.
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#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#include <string>
#include <iostream>

using namespace std;

// ------------------------------------------------------
const short SOCKET_ERROR = -1;

const short RECV_BUFFER_SIZE = 20;
const short REQUEST_BUFFER_SIZE = 255;

int sock;
char recv_buf [RECV_BUFFER_SIZE + 1];
char req_buf [REQUEST_BUFFER_SIZE + 1];

const static char REQUEST_TEMPLATE [] = 
{
	"GET %s HTTP/1.1\r\n"
	"Host: xxx.xxx.xxx\r\n" // should be replaced with a really host
	"Connection: Keep-Alive\r\n"
	"\r\n"
};

// ------------------------------------------------------
void create_socket ();
void download (const string& path, string& response);

// ------------------------------------------------------

int main (void)
{
	string first_addr = "/~pdu/index.html"; // should be replaced with a really URL
	string second_addr = "/~pdu/a.html"; // should be replaced with a really URL
	string response;

	create_socket ();
	download (first_addr, response);
	cout << response << endl << endl;
	response = "";
	download (second_addr, response);
	if (response.size() > 0)
	{
		cout << response << endl;
	}
	else
	{
		cout << "### The 2nd recv() failed to receive any bytes from the socket!" << endl << endl;
	}
	
	close (sock);

	return 0;
}

void create_socket ()
{
	struct sockaddr_in addr;

	// ------------------------------------------------------
	sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if(sock == SOCKET_ERROR)
    {
        perror ("Could not make a socket.\n");
		exit (-1);
    }

	cout << ">>> Socket created!" << endl;

	// ------------------------------------------------------
	struct hostent* host_info = gethostbyname("cse.unl.edu");	
	
	cout << ">>> DNS done!" << endl;

	long host_addr;

	/* copy address into long */
	memcpy(&host_addr, host_info->h_addr,
		host_info->h_length);

	/* fill address struct */
	addr.sin_addr.s_addr = host_addr;
	addr.sin_port = htons(80);
	addr.sin_family = AF_INET;

	// ------------------------------------------------------
	if( connect(sock, (struct sockaddr*)(&addr),
		sizeof(addr)) == SOCKET_ERROR )
    {
        perror("Could not connect to HTTP server.\n");
		exit (-1);
    }

	cout << ">>> Connection established!" << endl;
}

void download (const string& path, string& response) 
{
	size_t nBytes = snprintf(
		req_buf, 
		REQUEST_BUFFER_SIZE, 
		REQUEST_TEMPLATE, 
		path.c_str());

	if (nBytes >= REQUEST_BUFFER_SIZE)
	{
        cerr << "Buffer is too small for making a request message" << endl;
		exit (-1);
	}

	if (send(sock, req_buf, nBytes, 0) != nBytes)
	{
        perror("Could not send request to the HTTP server.\n");
		exit (-1);
	}
	cout << ">>> Request sent! -> " << path << endl << req_buf << endl;
	
	ssize_t size = 0;
	
	while ((size = recv(sock, recv_buf, 
		RECV_BUFFER_SIZE, 0)) > 0) 
	{
		recv_buf[size] = '\0';
		response.append(recv_buf);
    }

	cout << ">>> Response received!" << endl;
}