Linux网络编程——tcp套接字-编程知识

文章目录

主要代码
关于构造
listen监听
accept
telnet测试
读取信息
掉线重连
翻译服务器演示

本章Gitee仓库：tcp套接字

主要代码

客户端：

#pragma once#include"Log.hpp"#include<iostream>
#include<cstring>#include<sys/wait.h>
#include<unistd.h>
#include<signal.h>
#include<pthread.h>#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netinet/in.h>#include"threadPool.hpp"
#include"Task.hpp"const int defaultfd = -1;
const std::string defaultip = "0.0.0.0";
const int backlog = 5;  //不要设置太大
Log log;enum{USAGE_ERR = 1,SOCKET_ERR,BIND_ERR,LITSEN_ERR
};
class TcpServer;class ThreadData
{
public:ThreadData(int fd, const std::string &ip, const uint16_t &port, TcpServer *t):t_sockfd_(fd), t_clientip_(ip), t_clientport_(port), t_tsvr_(t){}
public:int t_sockfd_;std::string t_clientip_;uint16_t t_clientport_;TcpServer *t_tsvr_; //需要this指针
};class TcpServer
{public:TcpServer(const uint16_t &port, const std::string &ip = defaultip):listensockfd_(defaultfd),port_(port),ip_(ip){}//初始化服务器void Init(){//创建套接字listensockfd_ = socket(AF_INET, SOCK_STREAM, 0); //sock_stream提供字节流服务--tcpif(listensockfd_ < 0){log(Fatal, "create socket, errno: %d, errstring: %s",errno, strerror(errno));exit(SOCKET_ERR);}log(Info, "create socket success, sockfd: %d",listensockfd_);int opt = 1;setsockopt(listensockfd_, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt));  //防止偶发性服务器无法进行立即重启//本地套接字信息struct sockaddr_in local;memset(&local, 0, sizeof(local));//填充网络信息local.sin_family = AF_INET;local.sin_port = htons(port_);inet_aton(ip_.c_str(), &(local.sin_addr));//bindint bd = bind(listensockfd_, (struct sockaddr*)&local, sizeof(local));if(bd < 0){log(Fatal, "bind error, errno: %d, errstring: %s",errno, strerror(errno));exit(BIND_ERR);}log(Info, "bind success");//tcp面向连接, 通信之前要建立连接//监听if(listen(listensockfd_, backlog) < 0){log(Fatal, "listen error, errno: %d, errstring: %s",errno, strerror(errno));exit(LITSEN_ERR);}log(Info, "listen success");}static void *Routine(void *args){pthread_detach(pthread_self());//子线程无需关闭文件描述符ThreadData *td = static_cast<ThreadData*>(args);td->t_tsvr_->Service(td->t_sockfd_, td->t_clientip_, td->t_clientport_);delete td;}void Start(){signal(SIGPIPE, SIG_IGN);threadPool<Task>::GetInstance()->Start();//signal(SIGCHLD, SIG_IGN);  //直接忽略进程等待 V2log(Info, "server is running...");while(true){//获取新链接struct sockaddr_in client;socklen_t len = sizeof(client);int sockfd = accept(listensockfd_, (struct sockaddr*)&client, &len);if(sockfd < 0){log(Warning, "accpet error, errno: %d, errstring: %s",errno, strerror(errno));continue;}uint16_t clientport = ntohs(client.sin_port);char clientip[32];inet_ntop(AF_INET, &(client.sin_addr), clientip, sizeof(clientip));log(Info, "get a new link..., sockfd: %d, clientip: %s, clientport: %d", sockfd, clientip, clientport);//根据新链接进行通信//V1--单进程//Service(sockfd, clientip, clientport);//close(sockfd);//V2--多进程// pid_t id = fork();// if(id == 0)// {//     //child//     close(listensockfd_);  //子进程可以看到父进程的文件描述符表,关闭不需要的 //     if(fork() > 0)  exit(0);//父进程创建的子进程直接退出//     Service(sockfd, clientip, clientport);  //孙子进程执行, 由于孙子的父进程退出, 由系统领养//     close(sockfd);//     exit(0);// }// //father// close(sockfd);  //存在引用计数,不会这个关闭这个文件// pid_t tid = waitpid(id, nullptr, 0);// (void)tid;//V3--多线程(创建进程成本较高,换线程)// ThreadData *td = new ThreadData(sockfd, clientip, clientport, this);// pthread_t tid;// pthread_create(&tid, nullptr, Routine, td);//pthread_join(tid, nullptr);   //已进行线程分离,无需等待(并发执行)//V4--线程池Task t(sockfd, clientip, clientport);threadPool<Task>::GetInstance()->Push(t);//sleep(1); }}void Service(int sockfd, const std::string &clientip, const uint16_t &clientport){char buffer[4096];while(true){ssize_t n = read(sockfd, buffer, sizeof(buffer));if(n > 0){buffer[n] = 0;std::cout << "client say# " << buffer << std::endl;std::string echo_str = "tcpserver echo# ";echo_str += buffer;write(sockfd, echo_str.c_str(), echo_str.size());}else if(n == 0){log(Info, "%s:%d quit, server close sockfd: %d", clientip.c_str(), clientport, sockfd);break;}else{log(Warning, "read error, sockfd: %d, clientip: %s, clientport: %d", sockfd, clientip.c_str(), clientport);break;}memset(buffer, 0, sizeof(buffer));}}~TcpServer(){}
private:int listensockfd_;uint16_t port_;std::string ip_;
};

客户端：

#include<iostream>
#include<cstring>
#include<unistd.h>#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netinet/in.h>void Usage(const std::string &proc)
{std::cout << "\n\tUsage: " << proc << "serverip serverport" << std::endl;
}int main(int argc, char *argv[])
{if(argc != 3){Usage(argv[0]);exit(1);}std::string serverip = argv[1];uint16_t serverport = std::stoi(argv[2]);// 填充信息struct sockaddr_in server;memset(&server, 0, sizeof(server));server.sin_family = AF_INET;server.sin_port = htons(serverport);inet_pton(AF_INET, serverip.c_str(), &(server.sin_addr));//连接模块while (true){int sockfd = 0;int cnt = 5;bool isreconnect = false;sockfd = socket(AF_INET, SOCK_STREAM, 0);if (sockfd < 0){std::cerr << "socket error" << std::endl;return 1;}do{// tcp客户端也无需显示bind// 向目标发起连接(connect的时候进行自动随机bind)int cn = connect(sockfd, (struct sockaddr *)&server, sizeof(server));if (cn < 0){isreconnect = true;cnt--;  //重连5秒std::cerr << "connet error, reconnect: " << cnt << std::endl;close(sockfd);sleep(1);   //每隔一秒重连一次}else{break;}}while(cnt && isreconnect);if(cnt == 0){std::cerr << "server offline..." << std::endl;break;}//服务模块//while (true){std::string message;std::cout << "Please Enter# ";std::getline(std::cin, message);if (message.empty())continue;int wn = write(sockfd, message.c_str(), message.size());if (wn < 0){std::cerr << "write error" << std::endl;//break;}char inbuffer[4096];int rn = read(sockfd, inbuffer, sizeof(inbuffer));if (rn > 0){inbuffer[rn] = 0;std::cout << inbuffer << std::endl;}else{//break;}}close(sockfd);}return 0;
}

关于构造

关于构造和初始化，可以直接在构造的时候，将服务器初始化，那为什么还要写到init初始化函数里面呢？

构造尽量简单一点，不要做一些“有风险”的操作。

listen监听

tcp是面向连接的，通信之前要建立连接，服务器处于等待连接到来的状态：

#include <sys/types.h>
#include <sys/socket.h>
int listen(int sockfd, int backlog);

accept

获取新链接：

#include <sys/types.h>
#include <sys/socket.h>
int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);

后两个参数输出型参数，获取对方的信息

这里返回也是一个套接字，这和最开始创建的listensockfd_有什么区别呢？

这就好比去吃饭，门口有一个拉客的，问“帅哥，来不来我们这里吃饭啊”，如果你去了，那就是“欢迎光临，几位呀”，你回答“我和我女朋友”，然后这个人大喊“两位客人，来一个服务员”，这时候就来了一个服务员招呼你坐下，然后给你菜单，点完菜之后给你上菜；在这个期间站在门口的拉客的人，一直在招揽客人，有人来就喊服务员招招待，人家不来就继续拉。

listensockdf_就是这个拉客的，真正给我们提供服务的是accept返回的