Re: Sockets best for real-time?

"Guillem" <guillemvicens-nospam@xxxxxxxxxxxxxxxxxx> wrote in message
news:xn0enfizsdkovk002@xxxxxxxxxxxxxxxxxxxxxxxxx
Arthur Hoornweg wrote:

The disadvantage of UDP is that there's no guarantee that a packet
doesn't get lost.

that's the reason I did not even mention it. Personally I think this
point could be a serious problem for a RTS


It's worth clarifying this: Packet loss AT THE ETHERNET LEVEL is a fact of
life with ALL network protocols, including TCP. A dedicated full-duplex
point-to-point link between two machines should mean that packet loss is
'practically' not a problem, but you don't really have a true network then.

Where UDP and TCP differ is their approach to packet loss: TCP guarantees
data delivery by retransmitting lost packets, while UDP does not. You can
add simple retransmission capabilities to UDP protocols, particularly if you
just have a command-packet/response-packet style of comms. And TCP's secure
redelivery costs time and bandwidth.

With TCP, the time taken to deliver or receive a packet is essentially under
control of the network stack, not the programmer. With UDP, you can control
a lot more yourself, making it very suitable for many simple realtime
systems.

However, IMO, unless you absolutlely need the 'simplicity' and low-level
control that UDP (or your own IP-based protocol) gives you, stick with TCP.
And, if you want to optimise responsiveness with TCP/IP, you must understand
the Nagle (TCP_NODELAY) flag!

Either way, make sure you know how to use Ethereal. It will be your best
friend!

- Roddy




.

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