"PTY allocation request failed on channel 0"

[Ogogon !!! <ogogon@xxxxxxxxxx>]

Colleagues, please tell me the answer to my question.

*When I connecting to a test sshd-like programm, written using libssh, 
the client side gets the message "PTY allocation request failed on 
channel 0". Why is this happening? Was that intended?*

As test servers, I used programs samplesshd.c and samplesshd-tty.c
My OS - FreeBSD 11.4-RELEASE-p2 amd64
FreeBSD clang version 10.0.0 (git@xxxxxxxxxx 
<mailto:git@xxxxxxxxxx>:llvm/llvm-project.git llvmorg-10.0.0-0-gd32170dbd5b)
Target: x86_64-unknown-freebsd11.4
Thread model: posix
InstalledDir: /usr/bin
libssh-0.9.5
ssh client - OpenSSH_7.5p1, OpenSSL 1.0.2u-freebsd 20 Dec 2019 (on libssh2)

If I understand correctly, the message arrives after the message "it 
works !", when programm makе a call ssh_channel_read().
--
Thanks in advance for your reply,
Ogogon.