Edited Task: Can't connect [1237]

Hi,

We are using TFS 2013 Update 3 (are going to update to Update 4) but I can't connect.
I tried to adjust the settings file and to put it directly in the tool. Nothing works. Am I doing something wrong?
I tried the urls:
* http://servername:8080/tfs
* http://servername:8080/tfs/DefaultCollection