Re: [Boost-users] Monitor lost client data connections

Subject: Re: [Boost-users] Monitor lost client data connections
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2017-02-26 21:49:35

On 25/02/2017 09:33, jupiter via Boost-users wrote:
> Yes, I am also writhe the client program, each client has an unique
> identification and provides expecting only one connection per client.
> The client will auto-reconnect to the server if it detect lost
> connection, the question again, is writing to boost::asio::write the
> efficient way to detect a stalled connection or  are there any better
> alternatives to get feedback from the boost::asio::ip::tcp::socket
> lowest_layer? The problem is the client is always waiting receiving from
> server, if the client cannot detect from the oost::asio::ip::tcp::socket
> while waiting on boost::asio::read, then I have to run constantly
> heartbeat in every second or so which I try to avoid too much
> unnecessary bandwidth usage as the client is replying on LTE
> transmission, network bandwidth cost needs be considered.

As I understand it, the way that TCP itself works requires a 
transmission to detect a disconnected peer.

I haven't looked into how it's exposed in ASIO, but the sockopt I 
mentioned before is SO_KEEPALIVE -- it's basically just an automated 
periodic transmission.  A slight advantage of this over explicit writes 
is that the payload is a lot smaller, but it's still a packet.

If the client is expected to be using mobile Internet then to conserve 
both bandwidth and battery life you probably should not use any sort of 
keep-alive transmissions.  Instead design your server and protocol to 
expect that it won't really know how many clients are "really" connected 
at any given moment, and only discard a connection when you either have 
a fresh incoming one from the same client or if you failed to transmit.