@sharonyue Boo Hiss!! Well, nothing obvious so looks like somebody smarter than me is requisite for this one. ;(
Hmm... one last thing. Here's a netstat from Centos:
tcp 0 0 127.0.0.1:4569 0.0.0.0:* LISTEN
tcp6 0 0 :::22 :::* LISTEN
tcp6 0 0 ::1:25 :::* LISTEN
The first one is ipv4 while the last two ipv6. From your netstat I am unsure if your solr is listening to ipv4, as those multiple colons tend point to ipv6.
That you can telnet localhost would indicate things should work but I've no clue what NodeBB may be doing internally w.r.t. that stuff, so maybe a possibility?