When I open DayZ and hit "Play," I think the game connects to a random server. Once I'm connected to a server, how do I know which one I'm on? I couldn't find any menu that had the server info so I could let a friend know which one to join.
Find a safe location so you can minimize your game. Browse to My Documents -> DayZ and open username.DayZProfile with Notepad. Scroll down to the bottom of the file and it will show you...
LastMPServerName="Name of the last server you connected to"
This is the server you last played on which is the server you are currently in.
Additionally, this is the server you join when you click "Play" and NOT a random server. This allows you to quickly join the last server you played on if it is available.
This is the only way I have found to find out what server I am currently logged into.