SocketServer design

[Stuart]

I need to write a socket server that accepts around 100 connections, but
this could grow to a 1000, or more in time. The data throughput will be
minimal, mostly in short random bursts, but it's important those
connections stay active.

Having googled a bit, I understand there is a limit of 64 socket
connections in .NET? How do you overcome that? Should I be creating a
new Thread for every connection? It seems a bit wasteful, given the
small amounts of data. (as little as 30 bytes in a 2 minute burst).

Stuart.

 

[Chad Z. Hower aka Kudzu]

Having googled a bit, I understand there is a limit of 64 socket
connections in .NET? How do you overcome that? Should I be creating a

http://www.indyproject.org/ - Free with source.

new Thread for every connection? It seems a bit wasteful, given the
small amounts of data. (as little as 30 bytes in a 2 minute burst).

Depends. Can you use UDP or must it be TCP?


--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programming is an art form that fights back"

Make your ASP.NET applications run faster
http://www.atozed.com/IntraWeb/

 

[Stuart]

Having googled a bit, I understand there is a limit of 64 socket

http://www.indyproject.org/ - Free with source.

Looks interesting - Thanks. I would like to avoid a 3rd party library
if possible, as I may look at porting this over to Linux/Mono later.
Worth a look though.

Depends. Can you use UDP or must it be TCP?

Has to be TCP. I'm writing a gateway/proxy server for clients that
already exist.

S.

 

[Chad Z. Hower aka Kudzu]

Looks interesting - Thanks. I would like to avoid a 3rd party library
if possible, as I may look at porting this over to Linux/Mono later.
Worth a look though.

Its free - and has source. The .NET one is usuable, but very limited:
http://www.indyproject.org/Features.iwp

Has to be TCP. I'm writing a gateway/proxy server for clients that
already exist.

Once you are at about 1,000, threads definitely begin to become an issue. 99%
of servers should be threaded, but in your case Id prob place it in the 1%
that shouldnt be if its just doing the small data passing and not much
session logic.


--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programming is an art form that fights back"

Develop ASP.NET applications easier and in less time:
http://www.atozed.com/IntraWeb/

 

[Laxmikant Rashinkar]

I wrote a program that has 250 socket connections open simultaneously on the
server side
and it works just fine. I used a thread per connection. Although it was not
the ideal solution,
it still worked fine. I came across this article that might interest you:

http://www.eecs.harvard.edu/~mdw/proj/seda/#papers
http://www.eecs.harvard.edu/~mdw/papers/seda-sosp01.pdf

If you google on SEDA you will fiind a lot more info.

Hope it helps.
LK

 

[Chad Z. Hower aka Kudzu]

I wrote a program that has 250 socket connections open simultaneously on
the server side
and it works just fine. I used a thread per connection. Although it was
not the ideal solution,

205 threads is fine, but this user was talking 1,000. 1,000 is fine too, but
in his situation it didnt sound like a good match for threads anways.



--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programming is an art form that fights back"

Develop ASP.NET applications easier and in less time:
http://www.atozed.com/IntraWeb/

 

[William Stacey [MVP]]

You can have more then 64 open sockets. That begs a question on how many
you can actually create per process? Anyone know for sure or is limited
only by memory? You probably want to use a thread pool as others have said
if you will have that many connections at same time (or use async sockets
which some really like and others don't like so much). An interesting
server that uses this method is the open source Cassini Web server by MS.
Also used in their WebMatrix tool. IIRC, it uses the std thread pool to
queue connections and handle them via the queue. Worth looking at for tips
on how others approached the issue.

http://www.asp.net/Projects/Cassini/Download/
"Explore and Extend the Cassini Web Server"
http://www.devx.com/dotnet/Article/11711/0/page/1

 

[William Stacey [MVP]]

I like that second link. Thanks.

 

[Chad Z. Hower aka Kudzu]

You can have more then 64 open sockets. That begs a question on how many

64 sockets is a Windows limitation on how many sockets can be passed to
wait and other system calls, etc. The .NET socket component *may* have some
calls that are affected by this limit.

you can actually create per process? Anyone know for sure or is limited
only by memory? You probably want to use a thread pool as others have

said

Neither. Its limited by the size of the non-page pools. The size of the non
page pool depends on the OS and somewhat on RAM. But at max its never ever
more than 256 MB in Windows. Each socket varies in size depending on
options and whether its a client or a server socket. Min is 1.5k for
servers, 2k for clients. But typical is 4k.

if you will have that many connections at same time (or use async sockets
which some really like and others don't like so much). An interesting

1,000 is nothing to worry about.

server that uses this method is the open source Cassini Web server by MS.
Also used in their WebMatrix tool. IIRC, it uses the std thread pool to
queue connections and handle them via the queue. Worth looking at for
on how others approached the issue.

Wont work if he needs persistent connections, which based on the little bit
of info he provided probably does.


--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programming is an art form that fights back"

Get your ASP.NET in gear with IntraWeb!
http://www.atozed.com/IntraWeb/

 

[Stuart]

You can have more then 64 open sockets. That begs a question on how many
you can actually create per process?

Well it seems to be 64. Interestingly, if I run the same test program
binary on Linux/Mono, it bombs out at 1011 connections, not 64.

Stuart.

 

[William Stacey [MVP]]

Did I do the math correct? 262144K / 4K = ~65536 sockets.

 

[William Stacey [MVP]]

Well it seems to be 64.

Depends. As Chad said, you can only wait on 64 using one of the win32 wait
methods - that is were that number comes up. If the server is a
request/reply (i.e. web), then you can have much more by using a thread pool
or thread per connection. If you use an Async design, then you can also
have many more, as the IOCP thread pool handles the callbacks.

Interestingly, if I run the same test program
binary on Linux/Mono, it bombs out at 1011 connections, not 64.

What kind of server design? Seperate threads, thread pool, async? Sounds
like maybe a thread per connection design as around 1000 you start hitting a
memory issue as shown in prior posts.

 

[Stuart]

Interestingly, if I run the same test program

What kind of server design? Seperate threads, thread pool, async? Sounds
like maybe a thread per connection design as around 1000 you start hitting a
memory issue as shown in prior posts.

Single thread, using Socket.Select()
My code is very similar to this:
http://www.experts-exchange.com/Programming/Q_20803193.html
As you can see - this guy had the same problem.


Stuart.

 

[William Stacey [MVP]]

Check out the following:
"4.8 - How many simultaneous sockets can I have open with Winsock?"
"4.9 - What are the "64 sockets" limitations?"
http://tangentsoft.net/wskfaq/advanced.html#maxsockets

If you want to keep using Select(), it would seem you need to use multiple
threads and selecting on 64 per thread. That would seem to get messy so I
might instead go with async sockets or a threaded server if your connections
will be <= ~1000.

 

[peter markson]

FROM. FROM.PETER MARKSON
ADDRESS.MOTHER THREASA CAMP ABIDJAN COTE D'IVOIRE
TEL.22507557724
EMAIL ADDRESS. (e-mail address removed)

CONFIDENTIAL

Dear Sir,


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Best regards
PETER MARKSON

NB: my late father used me the only son as the beneficiary / next of kin
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