简单的HTTP获取与Winsock

Simple HTTP Get with Winsock

本文关键字：Winsock 获取 HTTP 简单      更新时间：2023-10-16

前段时间，我做了一个非常简单的方法，可以发出http请求并返回响应。这工作就像我的意图，但现在我想再次使用它，但我突然遇到了一个问题，我似乎无法弄清楚。每次我发出请求，它返回错误503:Service Unavailable.

有时起作用，有时不起作用。

我注意到，如果我在连接关闭后设置一个断点，然后稍等片刻然后继续，没有问题，一切正常。所以我的猜测是这与服务器的定时/延迟有关。

有人有这方面的经验吗?

提前感谢!

string HttpHelper::HttpGet(string host, string path)
{
    WSADATA wsaData;
    int result;
    // Initialize Winsock
    result = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (result != 0)
        throw SocketError(L"WSAStartUp", result);
    // Resolve the server address and port
    addrinfo * pAddrInfo;
    result = getaddrinfo(host.c_str(), "80", 0, &pAddrInfo);
    if (result != 0)
        throw SocketError(L"addrinfo", result);
    //Create the socket
    SOCKET sock = socket(pAddrInfo->ai_family, pAddrInfo->ai_socktype, pAddrInfo->ai_protocol);
    if (sock == INVALID_SOCKET)
        throw SocketError(L"Socket", WSAGetLastError());
    // Connect to server.
    result = connect(sock, pAddrInfo->ai_addr, pAddrInfo->ai_addrlen);
    if (result != 0)
        throw SocketError(L"Connect", WSAGetLastError());
    const string request = "GET " + path + " HTTP/1.1nHost: " + host + "nn";
    // Send an initial buffer
    result = send(sock, request.c_str(), request.size(), 0);
    if (result == SOCKET_ERROR)
        throw SocketError(L"Send", WSAGetLastError());
    // shutdown the connection since no more data will be sent
    result = shutdown(sock, SD_SEND);
    if (result == SOCKET_ERROR)
        throw SocketError(L"Close send connection", WSAGetLastError());
    // Receive until the peer closes the connection
    string response;
    char buffer[50];
    int bytesRecv = 0;
    for (;;)
    {
        result = recv(sock, buffer, sizeof(buffer), 0);
        if (result == SOCKET_ERROR)
            throw SocketError(L"Recv", WSAGetLastError());
        if (result == 0)
            break;
        response += string(buffer, result);
        wstringstream stream;
        stream << L"HttpGet() > Bytes received: " << bytesRecv;
        DebugLog::Log(stream.str(), LogType::INFO);
        bytesRecv += result;
    }
    wstringstream stream;
    stream << L"HttpGet() > Bytes received: " << bytesRecv;
    DebugLog::Log(stream.str(), LogType::INFO);
    // cleanup
    result = closesocket(sock);
    if (result == SOCKET_ERROR)
        throw SocketError(L"Closesocket", WSAGetLastError());
    result = WSACleanup();
    if (result == SOCKET_ERROR)
        throw SocketError(L"WSACleanup", WSAGetLastError());
    freeaddrinfo(pAddrInfo);
    DebugLog::Log(L"HttpGet() > Cleanup Successful ", LogType::INFO);
    return response;
}
wstring SocketError::ErrorMessage(const wstring & context, const int errorCode) const
{
    wchar_t buf[1024];
    FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, 0, errorCode, 0, buf, sizeof(buf), 0);
    wchar_t * newLine = wcsrchr(buf, 'r');
    if (newLine) *newLine = '';
    wstringstream stream;
    stream << L"Socket error in " << context << L" (" << errorCode << L"): " << buf;
    return stream.str();
}

不好说…

下面是一段简单而通用的winsock代码，你可以尝试一下，看看在使用这段代码时是否也存在这个问题。

#include <string.h>
#include <winsock2.h>
#include <windows.h>
#include <iostream>
#include <vector>
#include <locale>
#include <sstream>
using namespace std;
#pragma comment(lib,"ws2_32.lib")

string website_HTML;
locale local;
void get_Website(string url );
char buffer[10000];
int i = 0 ;

 //****************************************************
int main( void ){
    get_Website("www.stackoverflow.com" );
    cout<<website_HTML;
    cout<<"nnPress ANY key to close.nn";
    cin.ignore(); cin.get(); 

 return 0;
}
 //****************************************************
void get_Website(string url ){
    WSADATA wsaData;
    SOCKET Socket;
    SOCKADDR_IN SockAddr;
    int lineCount=0;
    int rowCount=0;
    struct hostent *host;
    string get_http;

    get_http = "GET / HTTP/1.1rnHost: " + url + "rnConnection: closernrn";
    if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0){
        cout << "WSAStartup failed.n";
        system("pause");
        //return 1;
    }
    Socket=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
    host = gethostbyname(url.c_str());
    SockAddr.sin_port=htons(80);
    SockAddr.sin_family=AF_INET;
    SockAddr.sin_addr.s_addr = *((unsigned long*)host->h_addr);
    if(connect(Socket,(SOCKADDR*)(&SockAddr),sizeof(SockAddr)) != 0){
        cout << "Could not connect";
        system("pause");
        //return 1;
    }
    send(Socket,get_http.c_str(), strlen(get_http.c_str()),0 );
    int nDataLength;
    while ((nDataLength = recv(Socket,buffer,10000,0)) > 0){        
        int i = 0;
        while (buffer[i] >= 32 || buffer[i] == 'n' || buffer[i] == 'r'){
            website_HTML+=buffer[i];
            i += 1;
        }               
    }
    closesocket(Socket);
    WSACleanup();
}

您必须以以下格式发送windows tcp套接字:

GET /romeo.txt HTTP/1.1rnHost: data.pr4e.orgrnrn
/romeo.txt是主机url的路径，data.pr4e.org是host

感谢某人:)

我将假设如果您将相同的主机名放入web浏览器，您将返回有效内容，而不是503。

三次随机猜测:

1)你需要一个User-Agent报头。将请求字符串构建为:

 const string request = "GET " + path + " HTTP/1.1n"
 request += "Host: " + host + "n";
 request += "User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36n";
 request += "n";

2)正如我在评论中提到的，确保send发送所有数据:

size_t sent = 0;
size_t remaining = request.size();
while (remaining > 0)
{
    const char* data = request.c_str() + sent;
    result = send(sock, data, remaining, 0);
    if (result == SOCKET_ERROR)
            throw SocketError(L"Send", WSAGetLastError());
    sent += result;
    remaining -= result;
}

3)唯一的其他事情可能是shutdown调用。

只是删除下面的行。从理论上讲，这不会有什么不同。但值得一试。

result = shutdown(sock, SD_SEND);
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