listen() function returns -1, however errno is set to 0

[seogyeongjeong]

I tried listen() function this way, however my echoserverfunction seems to have trouble in listen()
One thing I cannot understand is, errno is set to 0.
According to the manpage listen(2), if listen() returns -1 then errno will be set to indicate the error.
I have tried a lot of times to get over this. Can I get some hint?

Would this suggest that I might have converted appropriate IP address in a wrong way?

[Pusnow]

KENS does not support errno. Try non-kens version to debug this.

[seogyeongjeong]

Uhm, I'm so sorry but I tried non-kens version by
./app/echo/echo-non-kens s 127.0.0.1 9000 hello
And it shows the same result. (listen() function returns -1 and errno is set to 0).
:-(