How to prevent tcp port changes when connection fails

[denis_rda]

I have some client application written using boost::asio. I am trying to implement automatic reconnect when connection is lost. When connection can`t establishment (for example, when the server is unavailable) or connection issues I trying establish connection again. However, on each attempt, the application opens a new client port. This leads to a gradual usage of the all dynamic ports of the system.

class client
{
public:
client()
: socket_(nullptr)
, service_()
{
tcp::resolver r(service_);
auto iterator = r.resolve(tcp::resolver::query("127.0.0.1", "4572"));
if (iterator == tcp::resolver::iterator())
throw std::runtime_error("resolve");

endpoint_ = iterator->endpoint();
}

void start()
{
start_connect();
service_.run();
}

private:
void start_connect()
{
std::cout << "Trying " << endpoint_ << "...\n";

socket_ = std::make_shared<tcp::socket>(service_);

socket_->async_connect(endpoint_,
boost::bind(&client::handle_connect, this, _1));

}

void handle_connect(const boost::system::error_code& ec)
{
if (ec)
{
std::cout << "Connect error: " << ec.message() << "\n";
start_connect();
}
else
{
std::cout << "Connected to " << endpoint_ << "\n";
start_read();
}
}

void start_read()
{
boost::asio::async_read_until(*socket_, input_buffer_, '\n',
boost::bind(&client::handle_read, this, _1));
}

void handle_read(const boost::system::error_code& ec)
{
if (!ec)
{
std::string line;
std::istream is(&input_buffer_);
std::getline(is, line);

if (!line.empty())
std::cout << "Received: " << line << "\n";

start_read();
}
else
{
std::cout << "Error on receive: " << ec.message() << "\n";
start_connect();
}
}

private:
std::shared_ptr<tcp::socket> socket_;
boost::asio::io_service service_;
boost::asio::ip::tcp::endpoint endpoint_;
boost::asio::streambuf input_buffer_;
};

Is it possible to occupy only one client port for the entire execution time of the program? Or at least do not change the port for each attempt to connect to an unavailable server. I think explicit setting the client port is not good way. Tried not to re-create the socket every time but in this case it is impossible to re-establish the connection.

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