IPv4 fallback support is missing from ncat #157

quanah opened this Issue Jun 8, 2015 · 6 comments


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quanah commented Jun 8, 2015

As discussed in this thread from 2 years ago:

ncat does not have IPv4 fallback. This is a serious deficiency and lack of feature parity with the other nc implementation. It makes ncat essentially unusable on systems that have both ipv4 and ipv6 localhost defined, but only have services listening on the ipv4 localhost.

With only ipv4 localhost defined:

[root@zqa-226 ncat]# echo STATUS | ./ncat -w 15 localhost 7171
SUCCESS ACTIVE[root@zqa-226 ncat]#

After defining ::1 to localhost:

[root@zqa-226 ncat]# echo STATUS | ./ncat -w 15 localhost 7171
Ncat: Connection refused


+1 for getting this deficit fixed


see this email for updated patch with addressed comments http://seclists.org/nmap-dev/2015/q2/92

quanah commented Jun 16, 2015

I disagree that this is an "enhancement". This is a serious bug and lack of feature parity that causes serious issues when trying to use ncat as a replacement for nc.

d33tah commented Jul 2, 2015

I second @quanah.


Hello folks,
I have a small report regarding this please tell me if I am missing something and whether patch works fine or not.

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