any limitation on outbound tcp connections on Windows

Shelton Tang
Fri Jul 10 08:37:07 CEST 2009

I wrote a test program with C# and didn't see such problem. is this a
limitation in erlang@REDACTED?

On Fri, Jul 10, 2009 at 10:53 AM, Shelton Tang<> wrote:
> 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?
> Regards,
> Shelton

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