HttpUnderstanding.cpp

#include <winsock2.h>
#include <ws2tcpip.h>
#include <iostream>
#include <string>

#pragma comment(lib, "ws2_32.lib")

using namespace std;

void initWinsock(){
    WSADATA wsa;

    int result = WSAStartup(MAKEWORD(2,2),&wsa);
    if(result!=0){
        throw runtime_error("WSAStartup failed");
    }
}

addrinfo* resolveHost(const string &host, int port){
    addrinfo hints{};
    hints.ai_family = AF_INET; //IPV4
    hints.ai_socktype = SOCK_STREAM; // TCP

    addrinfo* result = nullptr;

    string portstr = to_string(port);

    int res = getaddrinfo(host.c_str(),portstr.c_str(),&hints,&result);

    if(res!=0){
        throw std::runtime_error("DNS resolution failed");
    }

    return result;
}

SOCKET connectSocket(addrinfo* addr){
    SOCKET sock = socket(
        addr->ai_family,
        addr->ai_socktype,
        addr->ai_protocol
    );

    if(sock == INVALID_SOCKET){
        throw runtime_error("Socket creation failed");
    }

    if(connect(sock,addr->ai_addr,(int)addr->ai_addrlen) == SOCKET_ERROR){
        closesocket(sock);
        throw runtime_error("Connection failed");
    }

    return sock;
}

string BuildHttpRequest(const string &host){
    string req;
    req += "GET /get HTTP/1.0\r\n";
    req += "Host: " + host + "\r\n";
    req += "Connection: close\r\n";
    req += "\r\n";
    return req;
}

void sendAll(SOCKET sock , const string &data){
    int totalSent = 0;
    int len = (int)data.size();

    while(totalSent < len){
        int sent = send(
            sock,
            data.c_str() + totalSent,
            len - totalSent,
            0
        );

        if(sent == SOCKET_ERROR){
            throw runtime_error("Send failed");
        }

        totalSent += sent;
    }
}

std::string receiveAll(SOCKET sock) {
    std::string response;
    char buffer[4096];

    while (true) {
        int received = recv(sock, buffer, sizeof(buffer), 0);
        if (received == 0) {
            break; // connection closed
        }
        if (received < 0) {
            throw std::runtime_error("Receive failed");
        }
        response.append(buffer, received);
    }

    std::cout << "Response size: " << response.size() << "\n";

    return response;
}

int main() {
    try {
        initWinsock();

        std::string host = "httpbin.org";
        int port = 80;

        addrinfo* addr = resolveHost(host, port);
        SOCKET sock = connectSocket(addr);

        std::string request = BuildHttpRequest(host);
        sendAll(sock, request);

        std::string response = receiveAll(sock);
        std::cout << response << "\n";

        closesocket(sock);
        freeaddrinfo(addr);
        WSACleanup();
    }
    catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << "\n";
    }
}