[JRuby] Thread blocked on `MessagePack::Unpacker.new(socket)`

[abbshr]

# jruby 9.1.13.0 (2.3.3)
sock = TCPSocket.new "localhost", 3000
u = MessagePack::Unpacker.new sock # => blocked here
# - unreachable, until remote endpoint close the connection -
u.each { |pack| p pack }

but if MessagePack::Unpacker.new(file_stream) is called on a file I/O stream, everything is ok

[chrisseaton]

Yeah isn't it blocked because it's trying to read from the socket? If you put some data into the socket from the other end does it work?