Can't access ports assigned to Rails 4.2, but 4.04 works fine

UnConundrum asked:

I have Ruby 2.1.2 installed and Rails 4.2.

Bundle install runs without error.

I can do a Rails C without error.

Rails s -p3004 launches with webrick or thin without error

When I browse to mytestsite:3004 safari, firefox, and chrome all report “can’t connect to server”

No errors show in any system logs; syslog, lfd.log, auth.log, or any of the apache logs.

If I launch my 4.04 site, ports 3001, 3002 work fine. If I bring down 4.04, and launch 4.2 on port 3001 or 3002, I get the ‘can not connect to server’ error. This seems to mean to me that it’s not a firewall issue blocking the port. Nonetheless, iptables -L reports that port 3004 is open:

ACCEPT     tcp  --  anywhere             anywhere             ctstate NEW tcp dpt:3004

Rails reports:

=> Booting WEBrick  
=> Rails 4.2.0.beta1 application starting in development on http://localhost:3004   
=> Run `rails server -h` for more startup options  
=> Ctrl-C to shutdown server  
[2014-09-02 21:31:06] INFO WEBrick 1.3.1  
[2014-09-02 21:31:06] INFO ruby 2.1.1 (2014-02-24) [x86_64-linux]  
[2014-09-02 21:31:06] INFO WEBrick::HTTPServer#start: pid=4599 port=3004  

(same result with thin).

Telnet localhost 3004 works from the server however telnet from another server to the port and ip address results in a connection refused.

and ps reports the program is loaded:

ps aux|grep 3004  
user 1062 0.0 0.5 578600 183996 pts/2 Sl+ 20:15 0:03 /home/user/.rvm/rubies/ruby-    2.1.1/bin/ruby bin/rails s -p3004

which is also confirmed by netstat:

netstat -tpln | grep 3004  
tcp 0 0* LISTEN 1062/ruby  

but mmap reports the port is closed:

Starting Nmap 6.40 ( ) at 2014-09-02 21:33 UTC  
Nmap scan report for localhost (  
Host is up (0.000059s latency).  
rDNS record for 127.0.x.1: local_host.local_domain  
3004/udp closed unknown  

And a telnet to the server 3004 reports connection refused.

Like I said, I’d think it was a firewall issue except that changing to port 3001, which I know to work with Rails 4.04, fails with 4.2. Anyone have any suggestions?

My answer:

WEBrick bound to rather than to INADDR_ANY, so you can only access it via that address. If you want to set what address it binds to, use the -b option. For example:

rails s -b -p 3004

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