A Teamspeak3 server uses the following ports:

Default port (incoming UDP): 9987
Default filetransfer port (incoming TCP): 30033
Default serverquery port (incoming TCP): 10011
Default weblist port (outgoing UDP): 2010
Default tsdns port (incoming TCP): 41144

If you have connection problems or problems with individual Teamspeak functions, you should check your firewall to ensure that these ports are open to the named protocol. Important: Many providers assign a port other than 9987 for the connection to the server! If you have connection problems, the cause might be that your Internet provider is blocking certain ports.