需要了解的知识

1. socket编程

2. socket select模型

3. request请求头与response响应头

4. c/c++中文件的读写操作

实现功能

1. 自动解析资源目录与请求参数

2. 自定义404页面

3. 实现基本的FTP服务

   #include <WinSock2.h>
   #include<iostream>
   #include<string>
   #include<unordered_map>
   #include<sstream>
   #pragma comment(lib,"ws2_32.lib")
   #pragma warning(disable:4996)
   using namespace std;
   unordered_map<string, string> contentType;
   void inItContentType(){//初始化contentType
    contentType["html"] = "text/html";
    contentType["txt"] = "text/plain";
    contentType["xml"] = "text/xml";
    contentType["gif"] = "image/gif";
    contentType["jpg"] = "image/jpeg";
    contentType["png"] = "image/png";
    contentType["mp3"] = "audio/mp3";
    contentType["mp4"] = "video/mpeg4";
   }
   bool Socket_Select(SOCKET hSocket, int  TimeOut = 100, bool Read = true) {  //封装select函数
    fd_set fdset; //socket自带的结构体 类似于队列
    timeval tv; //自带结构体
    FD_ZERO(&fdset);//清空
    FD_SET(hSocket, &fdset);//类似与入队
    tv.tv_sec = 0;
    tv.tv_usec = TimeOut;//超时时间
   
    int return_value;
    if (Read) {
        return_value = select(0, &fdset, NULL, NULL, &tv); //可读
    }
    else {
        return_value = select(0, NULL, &fdset, NULL, &tv);  //可写
    }
   
    if (return_value <= 0) return false;  //出现错误 或者无活动
    if (FD_ISSET(hSocket, &fdset)) return true;
    return false;
   }
   //读取文件
   string readFile(const char * const fileName, char **bufferPtr, int *size)
   {
    FILE * fp;
    fopen_s(&fp, fileName, "rb+");
    if (fp == nullptr)//未找到文件 寻找404文件
    {
        if ("404.html" == fileName){ //如果404文件也不存在 返回内置的错误页面
            *bufferPtr = new char[30];
            strcpy(*bufferPtr, "404 not found");
            *size = strlen(*bufferPtr);
            return "404 NotFound";
        }
        readFile("404.html", bufferPtr, size);
        return "404 NotFound";
    }
    fseek(fp, 0, SEEK_END);
    *size = ftell(fp);
    fseek(fp, 0, 0);
    *bufferPtr = new char[*size];
    fread(*bufferPtr, *size, 1, fp);
    fclose(fp);
    return "200 OK";
   }
   int main()
   {
    inItContentType();
    //请求版本
    WSADATA wsData;
    WSAStartup(MAKEWORD(2, 2), &wsData);
    if (HIBYTE(wsData.wVersion) != 2 || LOBYTE(wsData.wVersion) != 2)
    {
        cout << "版本请求失败" << endl;
        cin.get();
    }
    //创建socket
    SOCKET webServer = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);//IP4 TCP流传输 TCP协议
    if (SOCKET_ERROR == webServer)
    {
        cout << "socket创建失败" << endl;
        cin.get();
        return -1;
    }
    //创建协议地址族
    SOCKADDR_IN serverAddr;
    serverAddr.sin_family = AF_INET;//IP4
    serverAddr.sin_addr.s_addr = INADDR_ANY;//任意IP地址
    serverAddr.sin_port = htons(80);//监听端口转换  网络使用大端存储 电脑存储方式有大小端
    //socket与IP端口绑定
    if (bind(webServer, (SOCKADDR*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR)
    {
        cout << "绑定失败" << endl;
        cin.get();
        return -1;
    }
    //监听
    if (listen(webServer, 5) == INVALID_SOCKET) {
        cout << "设置监听状态失败！" << endl;
        return -1;
    }
    cout << "服务端正在监听...." << endl;
   
    //等待连接
    SOCKADDR_IN clientAddr;
    int len = sizeof(clientAddr);
    while (1)
   
    {
        SOCKET webClient = accept(webServer, (SOCKADDR*)&clientAddr, &len);
        try {
            if (webClient == -1)
            {
                cout << "连接失败" << endl;
            }
   
            //cout << inet_ntoa(clientAddr.sin_addr) << "请求了网页" << endl;
            char recvData[1024] = { 0 };
            string requestHeader = "";//请求头
            while (1){
                memset(recvData, 0, 1024);
                if (Socket_Select(webClient)){
                    int r = recv(webClient, recvData, 1024, 0);
                    if (r > 0)
                    {
                        requestHeader += recvData;
                    }
                    else{ //用户关闭了连接
                        throw "连接强制关闭";
                    }
                }
                else
                    break;
            }
   
            int fullPathStart = requestHeader.find("GET /") + 5;
            int fullPathEnd = requestHeader.find(" HTTP/1.1");
            if (-1 == fullPathStart || -1 == fullPathEnd) //没有接收到头文件
            {
   
                throw "资源路径有误";
            }
            string full_path = requestHeader.substr(fullPathStart, fullPathEnd - fullPathStart);//路径+参数
   
            string pathInfo;//路径
            string parameters="";//参数
            int parametersStart = full_path.find("?");
            if (-1 != parametersStart){//含有参数
                pathInfo = full_path.substr(0, parametersStart);
                parameters = full_path.substr(parametersStart);
                cout << pathInfo << endl << parameters << endl;
            }
            else{
                pathInfo = full_path;
            }
            if (-1 == pathInfo.find('.'))//路径中没有文件名 默认index.html
            {
                if (pathInfo.size() != 0 && pathInfo[pathInfo.size() - 1] != '/') //自动添加/
                    pathInfo += "/";
                pathInfo += "index.html";
            }
   
            //读取资源
            int size;
            char *Buffer = nullptr;
            string response_code = readFile(pathInfo.c_str(), &Buffer, &size);
            if (Buffer == nullptr)
            {
                throw "文件读取失败";
   
            }
            //根据文件名构造响应头
            string fileType = pathInfo.substr(pathInfo.rfind('.') + 1);
   
            string responseHeader = "HTTP/1.1 " + response_code + "\r\n" + "Content-Type: " + contentType[fileType] + ";\r\n\r\n";
            send(webClient, responseHeader.c_str(), responseHeader.size(), 0);
            send(webClient, Buffer, size, 0);
            delete[] Buffer;
        }
        catch (char *str){
            cout << "异常:" << str << endl;
        }
        closesocket(webClient);
    }
   }