前言

上一篇文章中，我们使用UDP协议编码完成了一个简单的服务器，实现数据通信，服务器设计出来后目的不仅仅只是实现数据通信，而是根据客户端发过来的请求，实现一定的需求，今天我们要介绍的是当客户端给服务端发送英文单词，然后服务端获取客户端的请求，将翻译结果返回给客户端，通过这样的方式，实现了一款英文翻译服务器。下面我们就一起具体来看看是如何编码完成。

1.设计思路：

如图所示

第一步：启动服务器，然后服务器加载词库

第二步：客户端向服务器，发送请求

第三步：服务器处理请求查找单词，将查找结果返回给客户端

第四步：客户端获取查询结果

2.词库设计

说明：在这里只是简单模拟实现一个词库，主要是实现业务逻辑

dict.txt:

aunt:姨母
brother:兄弟
cousin:堂兄弟
couple:夫妇
dad:爸爸
daughter:女儿
family:家
father:爸爸
grandchild:孙子
granddaughger:孙女
grandfather:祖父
grandma:外婆
grandpa:外公
granny	老奶奶

3.设计客户端

udpClient.hpp

#pragma once
#include <iostream>
#include <string>
#include <strings.h>
#include <cerrno>
#include <cstring>
#include <cstdlib>
#include <functional>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
namespace Client
{using namespace std;class udpClient{public:udpClient(const string &serverIp, const uint16_t serverPort): _serverIp(serverIp), _serverPort(serverPort), _sockfd(-1) {}void initClient(){_sockfd = socket(AF_INET, SOCK_DGRAM, 0);if (_sockfd == -1){cerr << "socket error:" << errno << strerror(errno) << endl;exit(2);}}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);while (1){string message;cout << "请输入你想要翻译的单词：";getline(cin,message);//发送请求sendto(_sockfd, message.c_str(), message.size(), 0, (const struct sockaddr *)&server, sizeof(server));char buffer[1024];struct sockaddr_in temp;socklen_t len = sizeof(temp);//接受查询翻译结果size_t n = recvfrom(_sockfd, buffer, sizeof(buffer) - 1, 0, (struct sockaddr *)&temp, &len);if (n >= 0)buffer[n] = 0;cout << "翻译的结果为: " << buffer << endl;}}private:string _serverIp;int _sockfd;uint16_t _serverPort;};
}

udpClient.cc:启动客户端

#include"udpClient.hpp"
#include<memory>
using namespace Client;
static void Usage(string proc)
{cout << "\nUsage:\n\t" << proc << " server_ip server_port\n\n";
}
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> uct(new udpClient(serverip,serverport));uct->initClient();uct->run();return 0;
}

4.设计服务端

udpServer.hpp

#pragma once
#include <iostream>
#include <string>
#include <strings.h>
#include <cerrno>
#include <cstring>
#include <cstdlib>
#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;const static string defaultIP = "0.0.0.0";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,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<<"socket error:" << errno << strerror(errno) << endl;exit(SOCKET_ERR);}struct sockaddr_in local;bzero(&local,sizeof(local));local.sin_family = AF_INET;local.sin_port = htons(_port);local.sin_addr.s_addr = htonl(INADDR_ANY);int n = bind(_sockfd,(struct sockaddr*)&local,sizeof(local));if(n == -1){cerr<<"bind error:" << errno << strerror(errno) << endl;exit(BIND_ERR);}}void startServer(){char buffer[1024];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){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;//服务器只负责接受数据，处理方法采用回调的方式交给上层处理_callback(_sockfd,clientIp,clientPort,message);}}}~udpServer(){}private:uint16_t _port;string _ip;int _sockfd;func_t _callback;};
}

udpServer.cc:启动服务端

#include "udpServer.hpp"
#include <memory>
#include <unordered_map>
#include <fstream>
using namespace Server;
static void Usage(string proc)
{cout << "\nUsage:\n\t" << proc << " local_port\n\n";
}
const string DictTxt = "./dict.txt";
unordered_map<string,string> dict;
static bool cutString(string& str,string& s1,string& s2,const string& sep)
{auto pos = str.find(sep);if(pos == string::npos)return false;s1 = str.substr(0,pos);s2 = str.substr(pos + sep.size());return true;
}
static void initDict()
{ifstream in(DictTxt,ios::binary);if(!in.is_open()){cerr << "open fail:" << DictTxt << "error" << endl;exit(OPEN_ERR);}string line;string key,value;while(getline(in,line)){if(cutString(line,key,value,":")){dict.insert(make_pair(key,value));}}in.close();cout << "load dict success" << endl;
}
//翻译：
void TranslationWord(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;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);}//加载词库initDict();uint16_t port = atoi(argv[1]);unique_ptr<udpServer> usvr(new udpServer(TranslationWord,port));usvr->initServer();usvr->startServer();return 0;
}

5.编译客户端和服务端

makefile:

.PHONY:all
all:udpServer udpClient
udpServer:udpServer.ccg++ -o $@ $^ -std=c++11
udpClient:udpClient.ccg++ -o $@ $^ -std=c++11.PHONY:clean
clean:rm -f udpServer udpClient