Ubuntu server 16.04.1 . I used ufw to open port 27015 (without specifying protocol, so both TCP and UDP), which is required for RCON access on Source servers. According to both ufw and iptables, port 27015 is open.
$ iptables -L -v -n
{snipping other unimportant rules}
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:27015
85 4505 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:27015
$ ufw status
Status: active
To Action From
-- ------ ----
{snipping other unimportant rules}
27015 ALLOW Anywhere
So according to my firewall, both tcp and udp, port 27015 is open.
However, every other application does not agree with this.
$ nmap localhost -p 27015
Starting Nmap 7.01 ( https://nmap.org ) at 2016-10-06 16:09 UTC
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00033s latency).
PORT STATE SERVICE
27015/tcp closed unknown
Nmap done: 1 IP address (1 host up) scanned in 0.08 seconds
Why is port 27015 closed on TCP? What can I do to actually open the port?
The server is hosted on DigitalOcean if that changes anything.