Not necessarily.
You could also set a proxy and connect thru the proxy in mIRC. (the data from your computer is routed thru the proxy, and it will appear to the IRC server that
To do this, simply go to a site like this:
http://www.publicproxyservers.com/index.html(Or search on google for "Public proxy" or something similar - what you are looking for is a list of public http proxy servers)
Look down the list on a page like that, most of those sites will have a list of which servers are operating properly.
Now start mIRC and go to File > Select Server. A window will pop up with a list on the left. Under Connect, go to the the item labeled Firewall. On the right, set "Firewall support" to "Server", protocol to "Proxy".
In the Hostname box, enter all the data to the left of the colon
: from the entry you have chosen from the list. (For example, if I chose 24.3.36.62:38884 I would enter
24.3.36.62 in the hostname box)
Make sure User ID and Password are blank (they aren't needed on public proxy servers.)
Go down to Port and enter anything that is to the right of the colon. (I would have entered
38884 if I used the proxy above).
Click OK at the bottom of the box, and try to go File > Connect to try again. (If connect is grayed out, click disconnect first, then try to reconnect)
It should establish a connection via the proxy and all should work fine. If it still won't let you connect, try a different proxy server.