该实例通过Socket模拟实现HTTP协议的GET请求方法，实现下载网页内容的功能。
头文件 downloader.h
#ifndef _DOWNLOADER_H_
#define _DOWNLOADER_H_
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <sys/time.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <iostream>
#include <string>
#include <stdexcept>
namespace httpget
{
class DOWNLOAD
{
public:
//downloader interface
static int DownLoader(std::string &textbuf, const std::string &uri);
private:
//separate host (domain) and path from uri
static void SepHostPath(const std::string &uri, std::string &host, std::string &path);
//resolve DNS
static int DnsResolve(const std::string &host, struct in_addr &ipaddr);
//readable data from connected server
static int Readable(int sock_id, struct timeval tv, int loops);
//control connect server time
static int TimeOut(int sock_id, struct timeval tv);
//create socket id
static int CreatSockId(int &sock_id);
//connect the web server
static int ConnectSer(int sock_id, const std::string &host, int port);
//send request information to the web server
static int SendMsg(int sock_id, const std::string &host, const std::string &path);
//get data from web server
static int RecvMsg(int sock_id, std::string &textbuf);
};
}
#endif
方法实现文件：downloader.cpp
#include "downloader.h"
namespace httpget
{
void DOWNLOAD::SepHostPath(const std::string &uri, std::string &host, std::string &path)
{
std::string::size_type pos = 0;
try
{
pos = uri.find("/", 8);
if(pos != std::string::npos)
{
host = uri.substr(7, pos-7);
path = uri.substr(pos);
}
else
{
host = uri.substr(7);
path = "/";
}
}
catch(std::out_of_range err)
{
host = "";
path = "";
}
}
int DOWNLOAD::TimeOut(int sock_fd, struct timeval tv)
{
fd_set rfdset;
int len = sizeof(int);
int error = -1;
bool ret;
FD_ZERO(&rfdset);
FD_SET(sock_fd, &rfdset);
if( select(sock_fd+1, NULL, &rfdset, NULL, &tv) > 0)
{
getsockopt(sock_fd, SOL_SOCKET, SO_ERROR, &error, (socklen_t *)&len);
if(error == 0)
ret = true;
else
ret = false;
}
else
ret = false;
if(!ret)
return -1;
else
return 1;
}
int DOWNLOAD::DnsResolve(const std::string &host, struct in_addr &ipaddr)
{
struct hostent *hp;
hp = gethostbyname(host.c_str());
if(!hp)
{
return -1;
}
ipaddr = *((struct in_addr *)hp->h_addr);
return 1;
}
int DOWNLOAD::Readable(int sock_fd, struct timeval tv, int loops)
{
int readen = 0;
int iter = 0;
fd_set rfdset;
FD_ZERO(&rfdset);
FD_SET(sock_fd, &rfdset);
for(; iter < loops; ++iter)
{
readen = select(sock_fd+1, &rfdset, NULL, NULL, &tv);
if(readen > 0 || (readen < 0 && errno != EINTR))
break;
sleep(1);
}
return readen;
}
int DOWNLOAD::CreatSockId(int &sock_fd)
{
if((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
return -1;
}
return 1;
}
int DOWNLOAD::ConnectSer(int sock_fd, const std::string &host, int port)
{
struct sockaddr_in serv_addr;
struct in_addr ipaddr;
int flag = 0;
struct timeval timeout;
ipaddr.s_addr = 0;
if(DnsResolve(host, ipaddr)==-1 || !(ipaddr.s_addr))
{
return -1;
}
bzero(&serv_addr, sizeof(struct sockaddr_in));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(port);
serv_addr.sin_addr = ipaddr;
if((flag = connect(sock_fd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr_in))) == -1)
{
if(errno == EINPROGRESS)
{
timeout.tv_sec = 5;
timeout.tv_usec = 0;
flag = TimeOut(sock_fd, timeout);
}
}
return flag;
}
int DOWNLOAD::SendMsg(int sock_fd, const std::string &host, const std::string &path)
{
char *request = NULL;
int len = 0;
try
{
len = host.length() + path.length() + 200;
request = new char[len];
memset(request, '\0', len);
sprintf(request, "GET %s HTTP/1.0\r\nHost: %s\r\n\r\n",path.c_str(), host.c_str());
strcat(request, "Accept: */*\r\n");
strcat(request, "User-Agent: Mozila/4.0(compatible; MSIE 5.0; Windows NT; DigExt; DTS Agent;)\r\n");
strcat(request, "Proxy-Connection: Keep-Alive\r\n");
strcat(request, "\r\n");
send(sock_fd, request, strlen(request), 0);
if(send(sock_fd, request, strlen(request), 0) == -1)
{
delete [] request;
request = NULL;
return -1;
}
delete [] request;
request = NULL;
return 1;
}
catch(std::bad_alloc err)
{
request = NULL;
return -1;
}
}
int DOWNLOAD::RecvMsg(int sock_fd, std::string &textbuf)
{
char *recvbuf = NULL;
try
{
struct timeval tv;
tv.tv_sec = 1;
tv.tv_usec = 0;
if(Readable(sock_fd, tv, 10) < 1)
{
return -1;
}
recvbuf = new char[10240];
memset(recvbuf, '\0', 10240);
int len = 0;
while(1)
{
if((len = recv(sock_fd, recvbuf, 10240, MSG_WAITALL)) > 0 )
{
recvbuf[len] = '\0';
textbuf += recvbuf;
memset(recvbuf, '\0', 10240);
}
else
{
break;
}
}
delete [] recvbuf;
recvbuf = NULL;
return 1;
}
catch(std::bad_alloc err)
{
recvbuf = NULL;
return -1;
}
}
int DOWNLOAD::DownLoader(std::string &textbuf, const std::string &uri)
{
std::string host(""), path("");
int sock_fd = 0;
SepHostPath(uri, host, path);
if(host.empty())
{
return -1;
}
if(CreatSockId(sock_fd) == -1)
{
return -1;
}
if(ConnectSer(sock_fd, host, 80) == -1)
{
close(sock_fd);
return -1;
}
if(SendMsg(sock_fd, host, path) == -1)
{
close(sock_fd);
return -1;
}
if(RecvMsg(sock_fd, textbuf) == -1)
{
close(sock_fd);
return -1;
}
close(sock_fd);
return 1;
}
}
测试文件：test.cpp
#include <iostream>
#include <string>
#include "downloader.h"
int main()
{
string webContent("");
string url("http://www.baidu.com");
httpget::DOWNLOAD::DownLoader(webContent, url);
cout << webContent << endl;
return 0;
}