Linux网络connect断线重连

Linux网络connect断线重连

1. 设计思路

用一个 enum class Status c++11 支持的强类型枚举，罗列所有连接可能的状态。

enum class Status // c++11 强类型枚举
{
    NEW,          // 新建状态，单纯的连接
    CONNECTING,   // 正在连接，仅用于查询conn状态
    CONNECTED,    // 连接或者重连成功
    DISCONNECTED, // 重连失败
    CLOSED        // 连接关闭，经历重连n次无法连接
};

强类型枚举要求使用时必须带上类的作用域，如 Status::NEW，能增加代码的可读性

在客户端的类中，设计 Execute() 执行连接所有可能的行为。当连接状态为 Status::NEW 时去进行连接， 当连接状态为 Status::CONNECTED 执行客户端的正常通信任务，当连接状态为 Status::DISCONNECTED 时，执行重连操作，当连接状态为 Status::CLOSED 重连失败，整个进程退出。

void Execute()
    {
        while (true)
        {
            switch (_conn.GetStatus())
            {
            case Status::NEW:
                _conn.Connect();
                break;
            case Status::CONNECTED:
                _conn.Process();
                break;

            case Status::DISCONNECTED:
                std::cout << "连接失败或对方掉线，开始重连" << std::endl;
                _conn.Reconnect();
                break;

            case Status::CLOSED:
                _conn.Disconnect();
                std::cout<<"重连失败，退出"<<std::endl;
                return;

            default:
                break;
            }
        }

其他看完整代码。

2. 完整代码

#include <iostream>
#include <cstring>
#include <string>
#include <unistd.h>
#include <cstdlib>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

void Usage(const std::string &process)
{
    std::cout << "Usage" << process << "server_ip server_port" << std::endl;
}

enum class Status // c++11 强类型枚举
{
    NEW,          // 新建状态，单纯的连接
    CONNECTING,   // 正在连接，仅用于查询conn状态
    CONNECTED,    // 连接或者重连成功
    DISCONNECTED, // 重连失败
    CLOSED        // 连接关闭，经历重连n次无法连接
};

class ClinetConnection
{
public:
    ClinetConnection(uint16_t serverport, std::string serverip)
        : _sockfd(-1),
          _serverport(serverport),
          _serverip(serverip),
          _retrt_interval(1),
          _max_retries(5),
          _status(Status::NEW)
    {
    }

    void Connect()
    {
        // 创建socket
        _sockfd = socket(AF_INET, SOCK_STREAM, 0);
        if (_sockfd < 0)
        {
            std::cerr << "sock error" << std::endl;
            exit(1);
        }

        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);

        int n = connect(_sockfd, (struct sockaddr *)&server, sizeof(server));
        if (n < 0)
        {
            Disconnect();
            _status = Status::DISCONNECTED;
            return;
        }
        _status = Status::CONNECTED;
    }

    Status GetStatus()
    {
        return _status;
    }

    void Disconnect()
    {
        if (_sockfd != 1)
        {
            close(_sockfd);
            _status = Status::CLOSED;
            _sockfd = -1;
        }
    }

    void Reconnect()
    {
        _status = Status::CONNECTING;
        int count = 0;
        while (count < _max_retries)
        {
            Connect();
            if (_status == Status::CONNECTED)
            {
                return;
            }
            sleep(_retrt_interval);
            count++;
            std::cout << "重连次数: " << count << "，最大上限: " << _max_retries << std::endl;
        }
        _status = Status::CLOSED; // 重连失败
    }

    void Process()
    {
         while (true)
        {
            std::string inbuffer;
            std::cout << "Please Enter# ";
            getline(std::cin, inbuffer);
            if(inbuffer.empty()) continue;
            
            ssize_t n = write(_sockfd, inbuffer.c_str(), inbuffer.size());
            if (n > 0)
            {
                char buffer[1024];
                ssize_t m = read(_sockfd, buffer, sizeof(buffer) - 1);
                if (m > 0)
                {
                    buffer[m] = 0;
                    std::cout << "echo messsge -> " << buffer << std::endl;
                }
                else if (m == 0) // 这里证明server端掉线了
                {
                    _status = Status::DISCONNECTED;
                    break;
                }
                else
                {
                    std::cout << "read m : " << m << "errno: " << errno << "errno string: " << strerror(errno) << std::endl;
                    _status = Status::CLOSED;
                    break;
                }
            }
            else
            {
                std::cout << "write n : " << n << "errno: " << errno << "errno string: " << strerror(errno) << std::endl;
                _status = Status::CLOSED;
                break;
            }
        }
    }

private:
    int _sockfd;
    uint16_t _serverport;
    std::string _serverip;
    int _retrt_interval; // 重试时间间隔
    int _max_retries;    // 重试次数
    Status _status;      // 连接状态
};

class TcpClient
{
public:
    TcpClient(uint16_t serverport, std::string &serverip) : _conn(serverport, serverip)
    {
    }
    void Execute()
    {
        while (true)
        {
            switch (_conn.GetStatus())
            {
            case Status::NEW:
                _conn.Connect();
                break;
            case Status::CONNECTED:
                _conn.Process();
                break;

            case Status::DISCONNECTED:
                std::cout << "连接失败或对方掉线，开始重连" << std::endl;
                _conn.Reconnect();
                break;

            case Status::CLOSED:
                _conn.Disconnect();
                std::cout<<"重连失败，退出"<<std::endl;
                return;

            default:
                break;
            }
        }
    }

private:
    ClinetConnection _conn;
};

int main(int argc, char *argv[])
{
    if (argc != 3)
    {
        Usage(argv[0]);
        return 1;
    }
    std::string serverip = argv[1];
    uint16_t serverport = std::stoi(argv[2]);
    TcpClient client(serverport, serverip);
    client.Execute();
    return 0;
}

3. 效果演示

重连失败：

重连成功：