If you've been lucky enough to have taken part in the much-hyped ARMS Global Testpunch then you may be a bit frustrated at the fact that trying to access the game outside of the scheduled online sessions results in an error message - the servers are only live at predetermined points.
However, Reddit user NefariousSquid has discovered an exploit which allows you to play the "warm up" segments of the game for a short period of time:
I've found a reliable way to play the "Warm-Up" mode accessible from online lobbies when the Testpunch server is offline, so you can practice outside of the event times! You'll need to have save data where you've gotten past the tutorial. (Because you can't access the tutorial unless the server is online, if you haven't been online in the Testpunch yet, you can't use this trick.)
1) On your Nintendo Switch, go to System Settings -> Internet -> Internet Settings -> [your network] -> Change Settings.
2) Enable proxy settings, and change the server address to
184.108.40.206(or some other fake address).
3) Save, then open the ARMS Global Testpunch.
4) Select Party Match, select a character, then go to Warm-Up.
You'll be able to play for 2 minutes and 30 seconds before it gives up on trying to connect to the non-existent proxy server and displays an error message. You can just close it and return to Warm-Up. Disable proxy settings from the same place you enabled them (System Settings -> Internet -> Internet Settings -> [your network] -> Change Settings) after you're done to return normal functionality to your Switch.
Here's a video of the exploit in action, courtesy of GameXplain:
While this is a long way from actually playing the game fully, it does at least allow you to get a feel for the controls and hone your skills in preparation for the next Testpunch session and the full release of the game.