翻译功能

我们写的UDP服务端并不是只接收到数据就完了，还需要进行处理任务。

我们可以在服务端udpServer.hpp中设置一个回调函数 _callback，具体的逻辑通过udpServer.cc中由外部进行传入

代码如下所示：

 		void start(){// 服务器的本质其实就是一个死循环char buffer[gnum];for(;;){// 读取数据struct sockaddr_in peer;socklen_t len = sizeof(peer); //必填ssize_t s = recvfrom(_sockfd, buffer, sizeof(buffer) - 1, 0, (struct sockaddr*)&peer, &len);if(s > 0){buffer[s] = 0;string clientip = inet_ntoa(peer.sin_addr); uint16_t clientport = ntohs(peer.sin_port);string message = buffer;cout << clientip <<"[" << clientport << "]# " << message << endl;//把收到的消息打印出来_callback(_sockfd, clientip, clientport, message);}}}

翻译功能:客户端输入一个单词，然后发送给服务端，然后去接收服务端翻译之后的结果。

首先提供一个字典dict:把鞋有英语和汉语对应的文件dicTxt加载进我们的unordered_map词典,此时的unordered_map就保存了字典的内容：

dict.txt:外部文件可由自己填写补充，这里只是给个样例测试代码而已

apple:苹果
world:世界
hello:你好
goodman:你是一个好人

const std::string dictTxt="./dict.txt";//文件
unordered_map<string, string> dict;//字典

下面，初始化我们的字典：打开文件，把文件中的每一行切分成key和value，也就是英文和中文，然后把结果插入到dict中，也就是把结果放进dict中，代码如下：

static bool cutString(const string &target, string *s1, string *s2, const string &sep)
{//apple:苹果auto pos = target.find(sep);if(pos == string::npos) return false;*s1 = target.substr(0, pos); //[)*s2 = target.substr(pos + sep.size()); //[）return true;
}static void initDict()
{ifstream in(dictTxt, std::ios::binary);if(!in.is_open()){cerr << "open file " << dictTxt << " error" << endl;exit(OPEN_ERR);}string line;std::string key, value;while(getline(in, line))//读取文件{if(cutString(line, &key, &value, ":")){dict.insert(make_pair(key, value));}}in.close();cout << "load dict success" << endl;
}

在udpServer.cc中通过函数handlerMessage处理数据，然后在把处理的结果反馈给客户端：

void handlerMessage(int sockfd, string clientip, uint16_t clientport, string message)
{string response_message;auto iter = dict.find(message);if(iter == dict.end()) response_message = "unknown";else response_message = iter->second;// 开始返回struct sockaddr_in client;bzero(&client, sizeof(client));client.sin_family = AF_INET;client.sin_port = htons(clientport);client.sin_addr.s_addr = inet_addr(clientip.c_str());sendto(sockfd, response_message.c_str(), response_message.size(), 0, (struct sockaddr*)&client, sizeof(client));
}

客户端udpClient.hpp输入消息cin并发送sendto给服务端，然后服务端udpServer.hpp调用回调函数对消息进行翻译，翻译完成后把最终的结果在传送sendto给客户端，客户端udpClient.hpp在接收recvfrom翻译之后的结果，最终把翻译结果打印出来即可:

 		void run(){struct sockaddr_in server;memset(&server, 0, sizeof(server));server.sin_family = AF_INET;server.sin_addr.s_addr = inet_addr(_serverip.c_str());server.sin_port = htons(_serverport);string message;char cmdline[1024];while (!_quit){cout<<"Please Enter#";cin>>message;sendto(_sockfd,message.c_str(),message.size(),0,(struct sockaddr*)&server,sizeof(server));char buffer[1024];struct sockaddr_in temp;socklen_t temp_len = sizeof(temp);size_t n = recvfrom(_sockfd,buffer,sizeof(buffer)-1,0,(struct sockaddr*)&temp,&temp_len);if(n>0) buffer[n] = 0;cout<<"服务器的翻译结果# "<<buffer<<endl;   }}

下面，进行测试运行结果:

//udpServer.cc
int main(int argc, char *argv[])
{if (argc != 2){Usage(argv[0]);exit(USAGE_ERR);}uint16_t port = atoi(argv[1]);initDict();std::unique_ptr<udpServer> usvr(new udpServer(handlerMessage, port));
}
//udpClient.cc
int main(int argc, char *argv[])
{if(argc != 3){Usage(argv[0]);exit(1);}string serverip = argv[1];uint16_t serverport = atoi(argv[2]);unique_ptr<udpClient> ucli(new udpClient(serverip, serverport));ucli->initClient();ucli->run();return 0;
}

先启动服务端：

在启动客户端输入信息，给服务端传送消息，服务端收到消息打印出来，并将翻译完成的结果返回给客户端，客户端再把翻译后的结果打印出来，这就是上面所说的整个过程：

命令行解析

借用popen接口：（功能相当于pipe+fork,exec*）

#include <stdio.h>
FILE *popen(const char *command, const char *type);
int pclose(FILE *stream);

command：传递进来的字符串，比如 ls -a -l ;type：以什么方式打开文件（r/w/a），我们通过一个函数execComand进行调用即可，只需要在udpServer.cc文件中修改传入的函数即可实现该功能：

void execCommand(int sockfd, string clientip, uint16_t clientport, string cmd)
{//1. cmd解析，ls -a -l//先禁止一下非法操作，防止有人搞破坏if(cmd.find("rm") != string::npos || cmd.find("mv") != string::npos || cmd.find("rmdir") != string::npos){cerr << clientip << ":" << clientport << " 正在做一个非法的操作: " << cmd << endl;return;}string response;FILE *fp = popen(cmd.c_str(), "r");if(fp == nullptr) response = cmd + " exec failed";char line[1024];while(fgets(line, sizeof(line), fp)){response += line;}pclose(fp);// 开始返回struct sockaddr_in client;bzero(&client, sizeof(client));client.sin_family = AF_INET;client.sin_port = htons(clientport);client.sin_addr.s_addr = inet_addr(clientip.c_str());sendto(sockfd, response.c_str(), response.size(), 0, (struct sockaddr*)&client, sizeof(client));
}

测试运行：

//udpServer.cc
int main(int argc, char *argv[])
{if (argc != 2){Usage(argv[0]);exit(USAGE_ERR);}uint16_t port = atoi(argv[1]);std::unique_ptr<udpServer> usvr(new udpServer(execCommand, port));
}

网络聊天室

我们需要去管理用户，而对于每个用户我们用IP和port来标识唯一性,那么多的用户我们可以用哈希表来进行统一管理：

class User
{
public:User(const string &ip, const uint16_t &port) : _ip(ip), _port(port){}~User(){}string ip(){ return _ip; }uint16_t port(){ return _port; }
private:string _ip;uint16_t _port;
};class OnlineUser
{
public:OnlineUser() {}~OnlineUser() {}void addUser(const string &ip, const uint16_t &port){string id = ip + "-" + to_string(port);users.insert(make_pair(id, User(ip, port)));}void delUser(const string &ip, const uint16_t &port){string id = ip + "-" + to_string(port);users.erase(id);}bool isOnline(const string &ip, const uint16_t &port){string id = ip + "-" + to_string(port);return users.find(id) == users.end() ? false : true;}void broadcastMessage(int sockfd, const string &ip, const uint16_t &port, const string &message){for (auto &user : users){struct sockaddr_in client;bzero(&client, sizeof(client));client.sin_family = AF_INET;client.sin_port = htons(user.second.port());client.sin_addr.s_addr = inet_addr(user.second.ip().c_str());string s = ip + "-" + to_string(port) + "# ";s += message;sendto(sockfd, s.c_str(), s.size(), 0, (struct sockaddr *)&client, sizeof(client));}}private:unordered_map<string, User> users;
};

在回调函数中，如果收到的消息是online，就把用户添加进哈希表。如果是offline，就从哈希表中删除

if (message == "online") onlineuser.addUser(clientip, clientport);
if (message == "offline") onlineuser.delUser(clientip, clientport);

OnlineUser onlineuser;
void routeMessage(int sockfd, string clientip, uint16_t clientport, string message)
{if (message == "online") onlineuser.addUser(clientip, clientport);if (message == "offline") onlineuser.delUser(clientip, clientport);if (onlineuser.isOnline(clientip, clientport)){// 消息的路由onlineuser.broadcastMessage(sockfd, clientip, clientport, message);}else{struct sockaddr_in client;bzero(&client, sizeof(client));client.sin_family = AF_INET;client.sin_port = htons(clientport);client.sin_addr.s_addr = inet_addr(clientip.c_str());string response = "你还没有上线，请先上线，运行: online";sendto(sockfd, response.c_str(), response.size(), 0, (struct sockaddr *)&client, sizeof(client));}
}

多线程：客户端udpClient.hpp不能立即收到消息打印出来，为了解决这个问题我们可以使用多线程，一个线程专门接收消息，一个线程专门发送消息:让主线程负责发送消息，子线程负责接收消息：

static void *readMessage(void *args){int sockfd = *(static_cast<int *>(args));pthread_detach(pthread_self());while (true){char buffer[1024];struct sockaddr_in temp;socklen_t temp_len = sizeof(temp);size_t n = recvfrom(sockfd, buffer, sizeof(buffer) - 1, 0, (struct sockaddr *)&temp, &temp_len);if (n >= 0)buffer[n] = 0;cout << buffer << endl;}return nullptr;}void run(){pthread_create(&_reader, nullptr, readMessage, (void *)&_sockfd);struct sockaddr_in server;memset(&server, 0, sizeof(server));server.sin_family = AF_INET;server.sin_addr.s_addr = inet_addr(_serverip.c_str());server.sin_port = htons(_serverport);string message;char cmdline[1024];while (!_quit){fprintf(stderr, "Enter# ");fflush(stderr);fgets(cmdline, sizeof(cmdline), stdin);cmdline[strlen(cmdline)-1] = 0;message = cmdline;sendto(_sockfd, message.c_str(), message.size(), 0, (struct sockaddr *)&server, sizeof(server));}}

UDP之Windows与Linux

UDP的实现可以在不同的平台上进行交互的，在这里我们以Linux充当服务端，windows充当客户端,进行连通

windows端代码：

#define _CRT_SECURE_NO_WARNINGS
#pragma warning(disable:4996)#include <iostream>
#include <string>
#include <cstring>
#include <WinSock2.h>#pragma comment(lib,"ws2_32.lib")using namespace std;
uint16_t serverport = 8080;
string serverip = "8.134.152.121";int main()
{WSAData wsd;if (WSAStartup(MAKEWORD(2, 2), &wsd) != 0){cout << "WSAStartup Error = " << WSAGetLastError() << endl;return 0;}else{cout << "WSAStartup Success" << endl;}SOCKET csock = socket(AF_INET, SOCK_DGRAM, 0);if (csock == SOCKET_ERROR){cout << "socket Error = " << WSAGetLastError() << endl;return 1;}else{cout << "socket success" << endl;}struct sockaddr_in server;memset(&server, 0, sizeof(server));server.sin_family = AF_INET;server.sin_port = htons(serverport);server.sin_addr.s_addr = inet_addr(serverip.c_str());
#define NUM 1024char inbuffer[NUM];string line;while (true){cout << "Please Enter#";getline(cin, line);int n = sendto(csock, line.c_str(), line.size(), 0, (struct sockaddr*)&server, sizeof(server));if (n < 0){cerr << "sendto error!" << endl;break;}struct sockaddr_in peer;int peerlen = sizeof(peer);inbuffer[0] = 0;n = recvfrom(csock, inbuffer, sizeof(inbuffer) - 1, 0, (struct sockaddr*)&peer, &peerlen);if (n > 0){inbuffer[n] = 0;cout << "server 返回的消息是#" << inbuffer << endl;}else break;}closesocket(csock);WSACleanup();return 0;
}

Linux端代码：

pragma once#include <iostream>
#include <string>
#include <strings.h>
#include <cerrno>
#include <cstring>
#include <functional>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>namespace Server
{using namespace std;static const string defaultIp = "0.0.0.0";static const int gnum = 1024;enum  {USAGE_ERR = 1,SOCKET_ERR,BIND_ERR,OPEN_ERR};typedef function<void (int,string,uint16_t,string)> func_t;class udpServer{public:udpServer(const func_t&cb,const uint16_t&port,const string&ip = defaultIp):_callback(cb),_port(port),_ip(ip),_sockfd(-1){}void initServer(){_sockfd = socket(AF_INET,SOCK_DGRAM,0);if(_sockfd == -1){cerr<<"sdocket error: "<<errno<<" : "<<strerror(errno)<<endl;exit(SOCKET_ERR);}cout<<"socket success: "<<" : "<<_sockfd<<endl;struct sockaddr_in local;bzero(&local,sizeof(local));local.sin_family = AF_INET;local.sin_port = htons(_port);local.sin_addr.s_addr = inet_addr(_ip.c_str());int n = bind(_sockfd,(struct sockaddr*)&local,sizeof(local));if(n == -1){cerr<<"bind errpr: "<<errno<<" : "<<strerror(errno)<<endl;exit(BIND_ERR);}}void start(){char buffer[gnum];for(;;){struct sockaddr_in peer;socklen_t len = sizeof(peer);ssize_t s = recvfrom(_sockfd,buffer,sizeof(buffer)-1,0,(struct sockaddr*)&peer,&len);if(s>0){buffer[s] = 0;string clientip = inet_ntoa(peer.sin_addr);uint16_t clientport = ntohs(peer.sin_port);string message = buffer;cout<<clientip<<"["<<clientport<<"]#"<< message<<endl;_callback(_sockfd,clientip,clientport,message);}}}~udpServer(){}private:int _sockfd;uint16_t _port;string _ip;func_t _callback;};
}
//udpServer.cc
#include <iostream>
#include <memory>
#include "udpServer.hpp"
using namespace std;
using namespace Server;static void Usage(string proc)
{cout<<"\nUsage:\n\t"<<proc<<" locla_port\n\n";
}void handlerMessage(int sockfd,string clientip,uint16_t clientport,string message)
{string response_message = message;response_message+=" [server echo]";struct sockaddr_in client;bzero(&client,sizeof(client));client.sin_family = AF_INET;client.sin_port = htons(clientport);client.sin_addr.s_addr = inet_addr(clientip.c_str());sendto(sockfd,response_message.c_str(),response_message.size(),0,(struct sockaddr*)&client,sizeof(client));
}int main(int argc,char*argv[])
{if(argc!=2){Usage(argv[0]);exit(USAGE_ERR);}uint16_t port = atoi(argv[1]);std::unique_ptr<udpServer> usvr(new udpServer(handlerMessage,port));usvr->initServer();usvr->start();return 0;
}