any limitation on outbound tcp connections on Windows

Shelton Tang
Fri Jul 10 04:53:04 CEST 2009

Hi All,

I use gen_tcp:connect to make outbound TCP connection.  The argument
passed to the call is  [list, {packet, 0},{reuseaddr, true},{active,
false}] (I also tried binary or passive mode but no luck).  However,
my test shows the maximum concurrent connections are <= 10 on my xp
and 5 - 8 on a X64 win2k8 machine. All other connections got timeout
error. So I captured a network traffic and didn't find any frame for
the timeout connections. Then I try to connect to the local host with On my WinXP box, I can create about 32 connections and
other got econnrefused error (the server is an erlang socket server).

I know there is a 10 SYN limitation on winxp tcpip.sys.  However, the
confused is why i hit the problem on a powerful (16G memory, 4
processors with dual cores) x64 machine? Possible reasons:
1. is there any limitation in erlang?  (becoz i can make > 10
connections to, most like it is not an erlang issue).
2. is there any limitation on tcpip.sys on win2k8?
3. is it possible there is a restraction on my firewall? (but if so, i
should see any network frames but actually i didn't find it).

any ideas?


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