Jabber screen share and firewall

[Phil Bradley]

I am trying to use jabber screen share between my local windows clients and it appears that it uses random ports to make the initial connection. I have referred to this document for the ports.

https://help.webex.com/en-us/WBX67527/What-Ports-does-Cisco-Jabber-Use

However, when I wireshark this I see the initial connection from the client using a random port below the ones listed of 49152–65535. It looks like the remote client viewing the screen does a three way handshake using the source range of 49152-65535 but the destination port is below this range. Windows firewall will block this inbound connection from the remote client so screen share fails. Is there a way to limit this port or tighten this up in the firewall? I do not want to allow inbound connections from internal clients from any port. Thanks!

[Jaime Valencia]

You should be able to configure that via the .xml, take a look at the parameter reference guide.

You also need 3389 which is the RDP port.

[Phil Bradley]

@Jaime Valencia I see were port screen share uses port 3389 in the documentation but I do not see this port being utilized when I share my screen. When I send the invitation to the other person they start a connection on a source random port 49152-65535 but the destination port is a random port below 49152. What am I missing?

[Jaime Valencia · Accepted solution]

Try the parameters to adjust the ports, if they're not being followed you might want to reach out to TAC for further investigation.

[Phil Bradley]

Thanks Jaime. I set the parameters and it appears to abide by these settings now. One thing that I did notice is that the minimum value for the range is 40.

[Sergio Quezada]

Hello Phil,

      Here is some documentation on this subject.

Screen Share:

https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/jabber/12_1/cjab_b_planning-guide-for-cisco-jabber/cjab_b_planning-guide-for-cisco-jabber_chapter_01001.html

Port Usage Information for the IM and Presence Service:
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/im_presence/configAdminGuide/11_5_1/CUP0_BK_CE08159C_00_config-admin-guide-imp-1151/CUP0_BK_CE08159C_00_config-admin-guide-imp-1151_chapter_011000.html

[Phil Bradley]

In case anyone else runs across this, the documentation is a little misleading. It states that the IM share uses RDP and while it may be using RDP it is not over port 3389. The remote client creates a connection to a random port and then uses TLS to the jabber process to share the screen. It may be using RDP over TLS but not over port 3389. If you do not define the port range like Jaime mentioned above, then I observed the connection on random ports below 49152 which is also misleading in the documentation.