最后我们可以根据上层的具体需求提供特定的 _OnMessage函数，我们这里就实现一个简单回声功能。

#include "TcpServer.hpp"
#include "Calculator.hpp"
#include <functional>
#include <memory>
void DefaultOnMessage(std::weak_ptr<Connection> conn)
{
    if (conn.expired())
        return;
    auto connection_ptr = conn.lock();
    Calculator calculator;
    std::string response_str = "echo $: ";
    std::cout << "上层得到了数据： " << connection_ptr->Inbuffer();
    response_str+=connection_ptr->Inbuffer();
    // response_str 发送出去
    connection_ptr->AppendOutBuffer(response_str);
    auto tcpserver = connection_ptr->_tcp_server_ptr.lock();
    tcpserver->Sender(connection_ptr);
}
int main(int argc, char *argv[])
{
    if (argc != 2)
    {
        Usage(argv[0]);
        exit(1);
    }
    uint16_t port = std::stoi(argv[1]);
    std::shared_ptr<TcpServer> Reactor(new TcpServer(port, DefaultOnMessage));
    Reactor->InitServer();
    Reactor->Loop();
    return 0;
}