Standard TSM client backups require setting the webports option to backup to TSM Server across a firewall, but the TSM client API does not support the webports option,
The tcpport option in the dsm.sys (default is 1500) is the only port that needs to be opened in the firewall to backup sysback to TSM.
Per Technote # 1307282: TSM client schedule and Web client setup in a firewall environment
Step 2. Open the following ports on the firewall to and from TSM server:
1500,tcp,out #TSM server port