it may be a firewall or antivirus issue
Which is why I asked if B3 and the other rcon tool were on the same box
@Op, got the e-mail.
Tested, b3 won't connect on my end either. So it is not a B3 config issue.
Then I tried a RCON tool for CoD6 and it won't connect either. It is the tool by d3ulxee and it on their forums.
Something in your rcon of your server is not working.