libtest-tcp-perl 2.19-1 (amd64 binary) in ubuntu bionic

 Test::TCP is a Perl test framework for TCP/IP programs, especially those
 written in Perl. For example, to test a client or server written in Perl,
 one simply specifies code to launch the server on an arbitrary port and
 provides corresponding code to execute a client to connect to it.
 .
 This module also supports running multiple servers in the same test file.