I can't connect to DirectAdmin on port 2222

If you are unable to access your server via http://1.2.3.4:2222, then 1 of 3 things is likely happening:

1. DirectAdmin might not be running or

2. You have a firewall blocking port 2222.

Number 2 is easy to check by simply running (only on redhat systems):

/sbin/service iptables stop
/sbin/chkconfig iptables off

Then test directadmin again.

If that didn't fix it, then you'd need to check your /var/log/directadmin/error.log to check for any errors as to why it isn't starting:

tail /var/log/directadmin/error.log

Common problems are:
3. Incorrect ethernet_dev set in the /usr/local/directadmin/conf/directadmin.conf file. guide

4. Invalid license, either due to wrong uid/lid, IP, or date.  Try: Updating your DirectAdmin License manually

5. Your IP is blacklisted in /usr/local/directadmin/data/admin/ip_blacklist.  This is controlled by the "brute force login detection" in Admin Settings.  Use a setting no lower than 10, since even loading the login page counts as 1 failed attempt.

6. Binaries for a different operating system. Related

You can always try running DirectAdmin by hand (if it's not already running) to see what the problem is.

cd /usr/local/directadmin
./directadmin b200

to start it in the terminal with debug level 200.  Use Ctrl-C to stop.

7. If DirectAdmin is running, is bound to port 2222, but doesn't respond on "127.0.0.1", but does respond on "::1", then it's an IPv6 issue.  This guide would be related.

---

CentOS 7
CentOS 7 uses a different method of firewall control.
To shut it off completely, type:

systemctl disable firewalld
systemctl stop firewalld

To just open port 2222, reported:

firewall-cmd --permanent --zone=public --add-port=2222/tcp