Linux 网络编程：理解 Web 路径与实现简单 HTTP 服务

void start() {
    listensock_.InitSocket(); // 初始化 sockfd
    listensock_.Bind(port_);  // 绑定
    listensock_.Listen();     // 监听
    for (;;) {
        string clientip;
        uint16_t clientport;
        int sockfd = listensock_.Accept(&clientip, &clientport);
        pthread_t tid;
        ThreadData* td = new ThreadData();
        td->sockfd = sockfd;
        pthread_create(&tid, nullptr, ThreadRun, td);
    }
}

ThreadRun

线程执行过程：创建缓冲区，从 sockfd 读取数据。

static void* ThreadRun(void* args) {
    pthread_detach(pthread_self());
    ThreadData* td = static_cast<ThreadData*>(args);
    char buffer[10240];
    ssize_t n = read(td->sockfd, buffer, sizeof(buffer) - 1);
    if(n > 0) {
        buffer[n] = 0;
        cout << buffer;
    }
    close(td->sockfd);
    delete td;
    return nullptr;
}

响应书写

可以将响应单独封装。HandlerHttp 函数负责接收请求并返回响应。

HTTP 响应格式：第一行是响应行，下面是多行报头，最后是空行和正文。

static void HandlerHttp(int sockfd) {
    char buffer[10240];
    ssize_t n = recv(sockfd, buffer, sizeof(buffer) - 1, 0);
    if(n > 0) {
        buffer[n] = 0;
        cout << buffer;

        string text = "hello world";
        string response_line = "HTTP/1.0 200 OK\r\n";
        string response_header = "Content-Length: ";
        response_header += to_string(text.size());
        response_header += "\r\n";
        string blank_line = "\r\n";

        string response;
        response += response_line;
        response += response_header;
        response += blank_line;
        response += text;

        send(sockfd, response.c_str(), response.size(), 0);
    }
    close(sockfd);
}

Web 路径

Web 根目录可以自定义，例如当前目录下的 wwwroot 文件夹。用户访问的 URL 路径对应服务器上的文件路径。

定义 Web 根目录：

const string wwwroot = "./wwwroot";

读取网页内容：

static string ReadWebContent(string path) {
    ifstream in(path);
    if (!in.is_open()) return "404";
    string content;
    string line;
    while (getline(in, line)) {
        content += line;
    }
    in.close();
    return content;
}

解析请求路径：

class Request {
public:
    void Deserialize(string req) {
        string tmp;
        int pos = 0;
        const string sep = "\r\n";
        while (true) {
            pos = req.find(sep);
            if (pos == string::npos) break;
            string temp = req.substr(0, pos);
            if (temp.empty()) break;
            req_header.push_back(temp);
            req.erase(0, pos + sep.size());
        }
        parse();
        text = req;
        DebugPrint();
    }

    void parse() {
        stringstream ss(req_header[0]);
        ss >> method >> url >> http_version;
        path = wwwroot;
        if (url == "/" || url == "/index.html") {
            path += "/";
            path += homepage;
        } else {
            path += url;
        }
    }

    void DebugPrint() {
        cout << "------------------------------------------------------------" << endl;
        for(auto& e : req_header) {
            cout << e << endl << endl;
        }
        cout << method << endl << url << endl << http_version << endl << path << endl;
        cout << text << endl;
    }

public:
    vector<string> req_header;
    string text;
    string method;
    string url;
    string http_version;
    string path;
};

完整代码示例：

#ifndef BE0E1813_421A_4BCD_A33B_77432A3CA8D7
#define BE0E1813_421A_4BCD_A33B_77432A3CA8D7
#include<iostream>
#include"Socket.hpp"
#include"Log.hpp"
#include<sstream>
#include<pthread.h>
#include<vector>
#include<fstream>

static const int defaultport = 8080;
const string wwwroot = "./wwwroot";
const string sep = "\r\n";
const string homepage = "index.html";

struct ThreadData {
    ThreadData(int sock) : sockfd(sock) {}
    int sockfd;
};

class Request {
public:
    void Deserialize(string req) {
        string tmp;
        int pos = 0;
        while (true) {
            pos = req.find(sep);
            if (pos == string::npos) break;
            string temp = req.substr(0, pos);
            if (temp.empty()) break;
            req_header.push_back(temp);
            req.erase(0, pos + sep.size());
        }
        parse();
        text = req;
        DebugPrint();
    }

    void parse() {
        stringstream ss(req_header[0]);
        ss >> method >> url >> http_version;
        path = wwwroot;
        if (url == "/" || url == "/index.html") {
            path += "/";
            path += homepage;
        } else {
            path += url;
        }
    }

    void DebugPrint() {
        cout << "------------------------------------------------------------" << endl;
        for(auto& e : req_header) {
            cout << e << endl << endl;
        }
        cout << method << endl << url << endl << http_version << endl << path << endl;
        cout << text << endl;
    }

public:
    vector<string> req_header;
    string text;
    string method;
    string url;
    string http_version;
    string path;
};

class HttpServer {
public:
    HttpServer(uint16_t port = defaultport) :port_(port) {}
    static string ReadWebContent(string str) {
        ifstream in(str);
        if (!in.is_open()) return "404";
        string content;
        string line;
        while (getline(in, line)) {
            content += line;
        }
        in.close();
        return content;
    }
    static void HandlerHttp(int sockfd) {
        char buffer[10240];
        ssize_t n = recv(sockfd, buffer, sizeof(buffer) - 1, 0);
        if(n > 0) {
            buffer[n] = 0;
            Request req;
            req.Deserialize(buffer);
            req.DebugPrint();

            string text = ReadWebContent(req.path);
            string response_line = "HTTP/1.0 200 OK\r\n";
            string response_header = "Content-Length: ";
            response_header += to_string(text.size());
            response_header += "\r\n";
            string blank_line = "\r\n";

            string response;
            response += response_line;
            response += response_header;
            response += blank_line;
            response += text;

            send(sockfd, response.c_str(), response.size(), 0);
        }
        close(sockfd);
    }
    static void* ThreadRun(void* args) {
        pthread_detach(pthread_self());
        ThreadData* td = static_cast<ThreadData*>(args);
        HandlerHttp(td->sockfd);
        delete td;
        return nullptr;
    }
    void start() {
        listensock_.InitSocket();
        listensock_.Bind(port_);
        listensock_.Listen();
        for (;;) {
            string clientip;
            uint16_t clientport;
            int sockfd = listensock_.Accept(&clientip, &clientport);
            pthread_t tid;
            ThreadData* td = new ThreadData(sockfd);
            td->sockfd = sockfd;
            pthread_create(&tid, nullptr, ThreadRun, td);
        }
    }
    ~HttpServer() {};
private:
    Socket listensock_;
    uint16_t port_;
};
#endif /* BE0E1813_421A_4BCD_A33B_77432A3CA8D7 */

通过以上步骤，我们实现了基于 C++ 的简单 HTTP 服务器，能够根据 Web 路径解析请求并返回对应的静态资源。