Re: Bug/Enhancement (ncat/nsock) - Recognize Winsock error codes

[David Fifield <david () bamsoftware com>]

On Thu, Nov 19, 2009 at 11:33:24AM +0000, Paul Milliken wrote:
> I've noticed that ncat doesn't interpret Windows Socket errors,
> instead displaying them as "Unknown error". Contrast the following
> outputs from Windows and Linux respectively:
>
> C:\tools\nmap-5.00>ncat -v -v -v 10.10.130.140 8888
> Ncat version 5.00 ( http://nmap.org/ncat )
> NSOCK (0.0620s) TCP connection requested to 10.10.130.140:8888 (IOD #1) EID 8
> NSOCK (1.0160s) Callback: CONNECT ERROR [Unknown error (10061)] for
> EID 8 [10.10.130.140:8888]
> DEBUG: Received callback of type CONNECT with status ERROR
>
> [paul.milliken@balamb ~]$ ncat -v -v -v 10.10.130.140 8888
> Ncat version 5.00 ( http://nmap.org/ncat )
> NSOCK (0.0020s) TCP connection requested to 10.10.130.140:8888 (IOD #1) EID 8
> NSOCK (0.0020s) Callback: CONNECT ERROR [Connection refused (111)] for
> EID 8 [10.10.130.140:8888]
> DEBUG: Received callback of type CONNECT with status ERROR
> Connection refused.
>
> According to MSDN, error code 10061 does indicate connection refused.
> It would more convenient if ncat interpreted the errors on Windows,
> especially when attempting to use it to diagnose connection issues.

Hi Paul, thanks for your suggestion. The next release of Ncat will have
this. When Ncat has a connection error, it will print the error even
without -v, and it will interpret the Windows error codes.

The Nsock messages don't interpret the Windows codes, because as I
recall those strings can be long and contain newlines. Nsock tracing is
a low-level option; we wanted to make the information from common
connection errors visible without excessive verbosity.

For other developers, when you want to print an error string, use the
socket_strerror function from nbase. The normal strerror function on
Windows doesn't interpret WinSock error codes. Windows also keeps its
error codes separate from the global errno, so you should use the
socket_errno function, also from nbase, to get it.

socket_strerror(socket_errno())

David Fifield
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