TCP客户端connect断线重连

1、为什么要断线重连

客户端会面临服务器崩溃的情况，我们可以试着写一个客户端重连的代码，模拟并理解一些客户端行为，比如游戏客户端等.

考虑到下面2种情况：

• 服务器故障突然断开连接，过几秒又恢复连接，那么在这等待的几秒，客户端可以重新发起连接。
• 客户端wifi突然断了，也就是没网，然后过几秒又恢复了，客户端又可以重新发起连接了。

2、实现代码

代码主要实现细节：

1. 枚举类型Status:

   • 用于表示连接状态，包括NEW, CONNECTED, CONNECTING, DISCONNECTED, CLOSE。

2. 全局常量:

   • defaultsockfd，默认套接字文件描述符为-1。

   • retryinterval，重连间隔时间为1秒。

   • retryamxtimes，重连最大次数为5次。

3. Connection类:

   • 构造函数初始化服务器IP、端口、状态、重连间隔和最大重连次数。

   • ConnectStatus()方法返回当前连接状态。

   • Connect()方法负责建立连接，并设置连接状态。

   • Process()方法负责发送和接收数据，处理通信过程中的各种状态变化。

   • ReConnect()方法处理重连逻辑，尝试在连接失败时进行多次重连。

   • DisConnect()方法负责断开连接并重置套接字文件描述符。

4. TcpClient类:

   • 构造函数初始化连接对象。

   • Execute()方法根据连接状态执行相应操作，包括建立连接、处理数据、重连和断开连接。

5. Usage()函数:

   • 用于输出使用说明。

6. main()函数:

   • 检查命令行参数，初始化TcpClient对象并执行连接逻辑。

• TcpClient.cc文件：

#include <iostream>
#include <string>
#include <strings.h>
#include <unistd.h>

#include "Comm.hpp"

enum class Status
{
   NEW,
   CONNECTED,
   CONNECTING,
   DISCONNECTED,
   CLOSE
};

const int defaultsockfd = -1;
const int retryinterval = 1; // 重连间隔时间
const int retryamxtimes = 5; // 重连最大次数

class Connection
{
public:
   Connection(std::string serverip, uint16_t serverport)
       : _sockfd(defaultsockfd),
         _serverip(serverip),
         _serverport(serverport),
         _status(Status::NEW),
         _retry_interval(retryinterval),
         _retry_max_times(retryamxtimes)
   {
   }

   Status ConnectStatus()
   {
       return _status;
   }

   void Connect()
   {
       _sockfd = socket(AF_INET, SOCK_STREAM, 0);
       if (_sockfd < 0)
       {
           _status = Status::DISCONNECTED;
           exit(CREATE_ERROR);
       }
       struct sockaddr_in server;
       bzero(&server, sizeof(server));
       server.sin_family = AF_INET;
       server.sin_port = htons(_serverport);

       // int inet_pton(int af, const char *src, void *dst);
       inet_pton(AF_INET, _serverip.c_str(), &server.sin_addr.s_addr); // 也可以&server.sin_addr，因为sin_addr只有s_addr
       int n = ::connect(_sockfd, CONV(&server), sizeof(server));
       if (n < 0)
       {
           DisConnect(); //
           _status = Status::DISCONNECTED;
           return;
       }
       std::cout << "connect success" << std::endl;
       _status = Status::CONNECTED; // 已连接
   }

   void Process()
   {
       while (true)
       {
           // 发送数据
           std::string message;
           std::cout << "Please Enter# ";
           std::getline(std::cin, message);
           int n = send(_sockfd, message.c_str(), message.size(), 0);
           if (n > 0)
           {
               // 接收数据
               char buff[1024];
               int m = recv(_sockfd, buff, sizeof(buff) - 0, 0);
               if (m > 0)
               {
                   buff[m] = 0;
                   std::cout << "Server Echo$ " << buff << std::endl;
               }
               else
               {
                   _status = Status::DISCONNECTED; // 接收不成功就重连
                   std::cerr << "recv error" << std::endl;
                   break;
               }
           }
           else
           {
               _status = Status::CLOSE; // 发送不成功就退出
               std::cerr << "send error" << std::endl;
               break;
           }
       }
   }

   void ReConnect()
   {
       _status = Status::CONNECTING;
       int cnt = 1;
       while (true)
       {
           Connect();
           if (_status == Status::CONNECTED)
           {
               break;
           }
           std::cout << "正在重连，重连次数 : " << cnt++ << std::endl;
           if (cnt > _retry_max_times)
           {
               _status = Status::CLOSE; // 重连失败
               std::cout << "重连失败，请检查网络.." << std::endl;
               break;
           }
           sleep(_retry_interval);
       }
   }

   void DisConnect()
   {
       if (_sockfd > defaultsockfd)
       {
           close(_sockfd);
           _sockfd = defaultsockfd;
       }
   }

private:
   int _sockfd;
   std::string _serverip;
   uint16_t _serverport;
   Status _status;
   int _retry_interval;
   int _retry_max_times;
};

class TcpClient
{
public:
   TcpClient(std::string serverip, uint16_t serverport) : _connect(serverip, serverport)
   {
   }
   void Execute()
   {
       while (true)
       {
           switch (_connect.ConnectStatus())
           {
           case Status::NEW:
               _connect.Connect();
               break;
           case Status::CONNECTED:
               _connect.Process();
               break;
           case Status::DISCONNECTED:
               _connect.ReConnect();
               break;
           case Status::CLOSE:
               _connect.DisConnect();
               return; // 断开连接了，重连不管用了
           default:
               break;
           }
       }
   }

private:
   Connection _connect;
};

void Usage()
{
   std::cout << "Please use format : ./tcp_client serverip serverport" << std::endl;
}

int main(int argc, char *argv[])
{
   if (argc != 3)
   {
       Usage();
       exit(USAGE_ERROR);
   }

   std::string serverip = argv[1];
   uint16_t serverport = std::stoi(argv[2]);

   TcpClient tcpclient(serverip, serverport);
   tcpclient.Execute();
   return 0;
}

和UDP服务器响应程序一样，客户端发什么就回什么，只不过多了建立连接的步骤。

• Comm.hpp文件

#pragma once
#include "InetAddr.hpp"

enum errorcode
{
  CREATE_ERROR = 1,
  BIND_ERROR,
  LISTEN_ERROR,
  SEND_ERROR,
  RECV_ERROR,
  CONNECT_ERROR,
  FORK_ERROR,
  USAGE_ERROR
};

#define CONV(ADDR) ((struct sockaddr *)ADDR)

std::string CombineIpAndPort(InetAddr addr)
{
  return "[" + addr.Ip() + ":" + std::to_string(addr.Port()) + "] ";
}

• InetAddr.hpp文件

#pragma once

#include <iostream>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string>

class InetAddr
{
  void GetAddress(std::string *ip, uint16_t *port)
  {
      // char *inet_ntoa(struct in_addr in);
      *ip = inet_ntoa(_addr.sin_addr);
      *port = ntohs(_addr.sin_port);
  }

public:
  InetAddr(const struct sockaddr_in &addr) : _addr(addr)
  {
      GetAddress(&_ip, &_port);
  }

  std::string Ip()
  {
      return _ip;
  }

  uint16_t Port()
  {
      return _port;
  }
  bool operator==(InetAddr &addr)
  {
      return _ip == addr.Ip() && _port == addr.Port();
  }

  const struct sockaddr_in& GetAddr()
  {
      return _addr;
  }

  ~InetAddr() {}

private:
  struct sockaddr_in _addr;
  std::string _ip;
  uint16_t _port;
};

• LockGuard.hpp文件

# pragma once

#include <pthread.h>


class LockGuard
{
public:
  LockGuard(pthread_mutex_t *mutex) : _mutex(mutex)
  {
      pthread_mutex_lock(_mutex); // 构造加锁
  }
  ~LockGuard()
  {
      pthread_mutex_unlock(_mutex); // 析构解锁
  }

private:
  pthread_mutex_t *_mutex;
};

• Log.hpp文件

#pragma once

#include <string>
#include <iostream>
#include <fstream>
#include <unistd.h>
#include <stdarg.h>
#include <sys/types.h>
#include "LockGuard.hpp"

using namespace std;

bool isSave = false; // 默认向显示器打印
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
#define FILEPATH "./log.txt"

enum level
{
  DEBUG = 0,
  INFO,
  WARNING,
  ERROR,
  FATAL
};

void SaveToFile(const string &message)
{
  ofstream out(FILEPATH, ios_base::app);
  if (!out.is_open())
      return;
  out << message;
  out.close();
}

std::string LevelToString(int level)
{
  switch (level)
  {
  case DEBUG:
      return "Debug";
  case INFO:
      return "Info";
  case WARNING:
      return "Warning";
  case ERROR:
      return "Error";
  case FATAL:
      return "Fatal";
  default:
      return "Unknow";
  }
}

std::string GetTimeString()
{
  time_t curr_time = time(nullptr);
  struct tm *format_time = localtime(&curr_time);
  if (format_time == nullptr)
      return "None";
  char buff[1024];
  snprintf(buff, sizeof(buff), "%d-%d-%d %d:%d:%d",
           format_time->tm_year + 1900,
           format_time->tm_mon + 1,
           format_time->tm_mday,
           format_time->tm_hour,
           format_time->tm_min,
           format_time->tm_sec);
  return buff;
}

void LogMessage(const std::string filename, int line, bool issave, int level, const char *format, ...)
{
  std::string levelstr = LevelToString(level);
  std::string timestr = GetTimeString();
  pid_t pid = getpid();

  char buff[1024];
  va_list arg;
  // int vsnprintf(char *str, size_t size, const char *format, va_list ap); // 使用可变参数
  va_start(arg, format);
  vsnprintf(buff, sizeof(buff), format, arg);
  va_end(arg);

  LockGuard lock(&mutex);
  std::string message = "[" + timestr + "]" + "[" + levelstr + "]" + "[pid:" + std::to_string(pid) + "]" + "[" + filename + "]" + "[" + std::to_string(line) + "] " + buff + '\n';
  if (issave == false)
      std::cout << message;
  else
      SaveToFile(message);
}

// 固定文件名和行数
#define LOG(level, format, ...)                                               \
  do                                                                        \
  {                                                                         \
      LogMessage(__FILE__, __LINE__, isSave, level, format, ##__VA_ARGS__); \
  } while (0)

#define EnableScreen()  \
  do                  \
  {                   \
      isSave = false; \
  } while (0)

#define EnableFile()   \
  do                 \
  {                  \
      isSave = true; \
  } while (0)

void Test(int num, ...)
{
  va_list arg;
  va_start(arg, num);
  while (num--)
  {
      int data = va_arg(arg, int);
      std::cout << data << " ";
  }
  std::cout << std::endl;
  va_end(arg);
}

• Main.cc文件

#include <iostream>
#include <memory>
#include "TcpServer.hpp"

void Usage()
{
  // printf("./udp_server serverip serverport\n");
  printf("Usage : ./udp_server serverport\n"); // ip 已经设置为0
}

int main(int argc, char *argv[])
{
  // if (argc != 3)
  if (argc != 2)
  {
      Usage();
      exit(USAGE_ERROR);
  }

  uint16_t serverport = std::stoi(argv[1]);
  std::unique_ptr<TcpServer> tsvr = std::make_unique<TcpServer>(serverport);
  tsvr->InitServer();
  tsvr->Start();

  return 0;
}

• Makefile文件

.PHONY:all
all:tcp_client tcp_server

tcp_client:TcpClient.cc
	g++ -o $@ $^ -std=c++14 -lpthread
tcp_server:Main.cc
	g++ -o $@ $^ -std=c++14 -lpthread

.PHONY:clean
clean:
	rm -f tcp_server tcp_client

• TcpServer.hpp文件

#pragma once

#include <sys/types.h> /* See NOTES */
#include <sys/wait.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#include <error.h>
#include <string.h>
#include <pthread.h>
#include <functional>

#include "Log.hpp"
#include "InetAddr.hpp"
#include "Comm.hpp"
#include "Threadpool.hpp"

const int defaultsockfd = -1;
int gbacklog = 16; // 暂时先用

using task_t = std::function<void()>;

// 声明
class TcpServer;

class ThreadData
{
public:
  ThreadData(int sockfd, InetAddr addr, TcpServer *self)
      : _sockfd(sockfd), _addr(addr), _self(self) {}
  ~ThreadData() = default;

public:
  int _sockfd;
  InetAddr _addr;
  TcpServer *_self;
};

class TcpServer
{
public:
  TcpServer(uint16_t port) : _port(port), _listensock(defaultsockfd), _isrunning(false)
  {
  }

  void InitServer()
  {
      // 创建
      _listensock = socket(AF_INET, SOCK_STREAM, 0); // 这个就是文件描述符
      if (_listensock < 0)
      {
          LOG(FATAL, "create sockfd error, error code : %d, error string : %s", errno, strerror(errno));
          exit(CREATE_ERROR);
      }
      LOG(INFO, "create sockfd success");

      struct sockaddr_in local;
      bzero(&local, sizeof(local));
      local.sin_family = AF_INET;
      local.sin_port = htons(_port);
      local.sin_addr.s_addr = INADDR_ANY;
      // 绑定
      int n = ::bind(_listensock, CONV(&local), sizeof(local));
      if (n < 0)
      {
          LOG(FATAL, "bind sockfd error, error code : %d, error string : %s", errno, strerror(errno));
          exit(BIND_ERROR);
      }
      LOG(INFO, "bind sockfd success");
  }

  void Service(int sockfd, InetAddr client)
  {
      while (true)
      {
          // TCP是字节流（可以使用write和read接口），UDP是数据报
          char buff[1024];
          // 接收消息
          int n = ::read(sockfd, buff, sizeof(buff)); // bug，接收数据可能收到的不完整，比如1+100，可能先收到1+1，再收到00 -- 按序到达
          std::string clientAddr = CombineIpAndPort(client);

          if (n > 0)
          {
              buff[n] = 0;
              std::string message = clientAddr + buff;
              LOG(INFO, "get message : \n %s", message.c_str());

              // 发送消息
              int m = ::write(sockfd, buff, strlen(buff)); 
              if (m < 0)
              {
                  LOG(FATAL, "send message error ,error code : %d , error string : %s", errno, strerror(errno));
                  exit(SEND_ERROR);
              }
          }
          else if (n == 0)
          {
              // 发送端不发送数据了
              LOG(INFO, "%s quit", clientAddr.c_str());
              break;
          }
          else
          {
              LOG(FATAL, "recv message error ,error code : %d , error string : %s", errno, strerror(errno));
              exit(RECV_ERROR);
          }
      }
      ::close(sockfd); // 服务结束，关闭文件描述符，避免文件描述符泄漏
  }

  static void *HandlerService(void *args)
  {
      pthread_detach(pthread_self()); // 分离线程
      ThreadData *td = static_cast<ThreadData *>(args);
      td->_self->Service(td->_sockfd, td->_addr);
      delete td;
      return nullptr;
  }

  void Start()
  {
      _isrunning = true;
      while (_isrunning)
      {
          // 监听
          int ret = ::listen(_listensock, gbacklog);
          if (ret < 0)
          {
              LOG(FATAL, "listen error, error code : %d , error string : %s", errno, strerror(errno));
              exit(LISTEN_ERROR);
          }
          LOG(INFO, "listen success!");

          struct sockaddr_in peer;
          socklen_t len = sizeof(peer);
          // 获取新连接
          int sockfd = accept(_listensock, CONV(&peer), &len); // 建立连接成功，创建新文件描述符进行通信
          if (sockfd < 0)
          {
              LOG(WARNING, "accept error, error code : %d , error string : %s", errno, strerror(errno));
              continue;
          }
          LOG(INFO, "accept success! new sockfd : %d", sockfd);

          InetAddr addr(peer); // 给后面提供传入的ip、port
          // 服务 -- 发送和接收数据
          // V0 -- 单进程
          // Service(sockfd, addr); // 这里是while死循环，没有运行完就一直运行，下一个请求来的时候得这个while退出才能执行

          // v1 -- 多进程
          // int id = fork();
          // if (id == 0)
          // {
          //     // 子进程
          //     ::close(_listensock); // 子进程对监听文件描述符不关心
          //     if (fork() > 0)
          //         exit(0);           // 子进程创建进程后退出，孙子进程被系统领养，不用等待
          //     Service(sockfd, addr); // 孙子进程执行任务
          //     exit(0);
          // }
          // else if (id > 0)
          // {
          //     ::close(sockfd); // 这里每次关闭的文件描述符都是4，使得每次accept创建的文件描述符都是4，这个4是留个各个子进程（子进程再给孙子进程）的（互不影响）
          //     // 父进程
          //     pid_t rid = waitpid(id, nullptr, 0); // 虽然是阻塞等待，但是子进程是刚创建就退出来了，让孙子进程（孤儿进程）执行任务，接下来继续监听和建立连接
          //     if (rid == id)
          //     {
          //         LOG(INFO, "wait child process success");
          //     }
          // }
          // else
          // {
          //     // 异常
          //     LOG(FATAL, "fork error ,error code : %d , error string : %s", errno, strerror(errno));
          //     exit(FORK_ERROR);
          // }

          // v2 -- 多线程
          // pthread_t tid;
          // ThreadData *td = new ThreadData(sockfd, addr, this); // 传指针
          // pthread_create(&tid, nullptr, HandlerService, td); // 这里创建线程后，线程去做执行任务，主线程继续向下执行 , 并且线程不能关闭sockf，线程和进程共享文件描述符表

          // v3 -- 线程池
          task_t t = std::bind(&TcpServer::Service, this, sockfd, addr);
          Threadpool<task_t>::GetInstance()->Enqueue(t);

          // v4 -- 进程池 -- 不推荐，需要传递文件描述符！
      }
      _isrunning = false;
  }

  ~TcpServer()
  {
      if (_listensock > defaultsockfd)
          ::close(_listensock); // 不用了关闭监听
  }

private:
  uint16_t _port;
  int _listensock;
  bool _isrunning;
};

• Thread.hpp文件

#ifndef __THREAD_HPP__
#define __THREAD_HPP__

#include <iostream>
#include <string>
#include <unistd.h>
#include <functional>
#include <pthread.h>

using namespace std;

// 封装Linux线程
namespace ThreadModule
{
  using func_t = function<void(string &)>;
  class Thread
  {
  public:
      // /* ThreadData* */Thread(func_t<T> func, T data, const string& name = "default name") : _func(func), _data(data), _threadname(name), _stop(true) {}
      Thread(func_t func, const string &name = "default name") : _func(func), _threadname(name), _stop(true) {}

      void Execute()
      {
          _func(_threadname);

          // _func(_data);
      }

      //  隐含this
      static void *threadroutine(void *arg)
      {
          Thread *self = static_cast<Thread *>(arg);
          self->Execute(); // static 访问不了成员变量
          return nullptr;
      }
      bool Start()
      {
          int n = pthread_create(&_tid, nullptr, threadroutine, this);
          if (!n)
          {
              _stop = false;
              return true;
          }
          else
          {
              return false;
          }
      }

      void Detach()
      {
          if (!_stop)
          {
              pthread_detach(_tid);
          }
      }

      void Join()
      {
          if (!_stop)
          {
              pthread_join(_tid, nullptr);
          }
      }

      string name()
      {
          return _threadname;
      }

      void Stop()
      {
          _stop = true;
      }
      // ~Thread() {}

  private:
      pthread_t _tid;
      string _threadname;
      func_t _func;
      bool _stop;
  };

} // namespace ThreadModule

#endif

• Threadpool.hpp文件

#pragma once

#include <vector>
#include <queue>
#include <queue>
#include "Thread.hpp"
#include <pthread.h>
#include "LockGuard.hpp"

using namespace ThreadModule;

const int NUM = 3;

template <typename T>
class Threadpool
{
  void LockQueue(pthread_mutex_t &mutex)
  {
      pthread_mutex_lock(&mutex);
  }

  void UnLockQueue(pthread_mutex_t &mutex)
  {
      pthread_mutex_unlock(&mutex);
  }

  void SleepThread(pthread_cond_t &cond, pthread_mutex_t &mutex)
  {
      pthread_cond_wait(&cond, &mutex);
  }
  void WakeUpThread(pthread_cond_t &cond)
  {
      pthread_cond_signal(&cond);
  }
  void WakeUpAll(pthread_cond_t &cond)
  {
      pthread_cond_broadcast(&_cond);
  }
  Threadpool(const int threadnum = NUM) : _threadnum(threadnum), _waitnum(0), _isrunning(false)
  {
      pthread_mutex_init(&_mutex, nullptr);
      pthread_cond_init(&_cond, nullptr);
      LOG(INFO, "Threadpool Constructor successful ! ");
  }

  void TaskHandler(string &name)
  {
      // sleep(1);
      // cout  << name << " : hh " << endl;
      // sleep(1);
      LOG(DEBUG, "%s is running", name.c_str());
      while (true)
      {
          LockQueue(_mutex);
          while (_task_queue.empty() && _isrunning)
          {
              // 等待
              ++_waitnum;
              SleepThread(_cond, _mutex);
              --_waitnum;
          }
          // 此时一定大于一个线程没有休眠
          if (_task_queue.empty() && !_isrunning)
          {
              // 此时任务队列已经没有内容，且此时线程池已经停止
              UnLockQueue(_mutex);
              cout << name << " quit ... " << endl;
              break;
          }
          LOG(DEBUG, "%s get task sucessful !", name.c_str());
          //  其他情况就得处理任务
          T t = _task_queue.front();
          _task_queue.pop();
          UnLockQueue(_mutex);

          // 处理任务
          t();
          // cout << name << " : " << t.stringResult() << endl;
          // LOG(DEBUG, "%s handler task sucessful ! Result is %s", name.c_str(), t.stringResult().c_str());
          sleep(1);
      }
  }
  void InitThreadPool()
  {
      for (int i = 0; i < _threadnum; ++i)
      {
          string name = "Thread - " + to_string(i + 1);
          _threads.emplace_back(bind(&Threadpool::TaskHandler, this, placeholders::_1), name);
      }
      _isrunning = true;
      LOG(INFO, "Init Threadpool successful !");
  }

public:
  static Threadpool<T> *GetInstance(int threadnum = NUM)
  {

      if (_instance == nullptr)
      {
          LockGuard lockguard(&_lock);
          if (_instance == nullptr)
          {
              // pthread_mutex_lock(&_lock);
              // 第一次创建线程池
              _instance = new Threadpool<T>(threadnum);
              _instance->InitThreadPool();
              _instance->Start();
              LOG(DEBUG, "第一次创建线程池");
              // pthread_mutex_unlock(&_lock);
              return _instance;
          }
      }

      LOG(DEBUG, "获取线程池");
      return _instance;
  }

  bool Enqueue(const T &in)
  {
      bool ret = false;
      LockQueue(_mutex);
      if (_isrunning)
      {
          _task_queue.push(in);
          if (_waitnum > 0)
              WakeUpThread(_cond);
          LOG(DEBUG, "enqueue sucessful...");
          ret = true;
      }

      UnLockQueue(_mutex);
      return ret;
  }

  void Stop()
  {
      LockQueue(_mutex);
      _isrunning = false;
      if (_waitnum > 0)
          WakeUpAll(_cond);
      UnLockQueue(_mutex);
  }

  void Start()
  {
      for (auto &thread : _threads)
      {
          thread.Start();
          LOG(INFO, "%s is start sucessful...", thread.name().c_str());
      }
  }

  void Wait()
  {
      for (auto &thread : _threads)
      {
          thread.Join();
          LOG(INFO, "%s is quit...", thread.name().c_str());
      }
  }
  ~Threadpool()
  {
      pthread_mutex_destroy(&_mutex);
      pthread_cond_destroy(&_cond);
      LOG(INFO, "delete mutex sucessful !");
  }

private:
  vector<Thread> _threads;
  queue<T> _task_queue;
  int _threadnum;
  int _waitnum;

  pthread_mutex_t _mutex; // 互斥访问任务队列
  pthread_cond_t _cond;

  bool _isrunning;

  // 懒汉模式
  static Threadpool<T> *_instance;
  static pthread_mutex_t _lock;
};

template <typename T>
Threadpool<T> *Threadpool<T>::_instance = nullptr;
template <typename T>
pthread_mutex_t Threadpool<T>::_lock = PTHREAD_MUTEX_INITIALIZER;

运行结果：

OKOK，TCP客户端connect短线重连就到这里，如果你对Linux和C++也感兴趣的话，可以看看我的主页哦。下面是我的github主页，里面记录了我的学习代码和leetcode的一些题的题解，有兴趣的可以看看。

Xpccccc的github主页