[fpc-pascal]Synapse for FPC

Matt Emson memsom at interalpha.co.uk
Wed Jul 23 12:12:39 CEST 2003

> Why must I use threads?

You must use threads in blocking tcp/ip else you will hang your application
everytime the network traffic slows or the application you connect to
(server?) does not immediately respond. Try changing your calls to blocking
and see what happens.

> Following works perfectly for me for many years:
> ioctl(Sock,FIONBIO, at tmp); // nonblocking
> All but one applications are single thread.

Yes. You are using the 'work around'. Traditional UNIX sockets block.
Microsoft (and others) realised this would not work with a co-operative
multitasking operating system (e.g. Windows 3.1, MacOS 9 and prior) and so
the idea of non-blocking sockets was concieved. Indeed M$'s first Winsock
implementations used purely Non-blocking sockets.

The tcp/ip developer has two avenues to wander down. Use threads and
blocking api. It's fast and responsive and we only have to worry about
sharing data between threads, or use non-blocking code and then have to work
around the fact that tcp/ip can be slow and we will not get all my data in
one big chunk. Using Non blocking sockets means that your code becomes more
complex and convoluted because you may well have to go through the event
look many hundreds of times before your download or upload has completed.
Using multiple threads, you simple hand the data over to the thread when
uploading and either carry on. Downloading you simply send a message to the
main thread when the data is ready. It's also easy to simulate non-blocking
sockets with blocking code using threads. This gives you a clear seperation
between your tcp/ip mechanism and your application code. This is the route
we usually take here.

Swings and roundabouts, I know ;-)


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