MessageHTTPUploader.performUpload: [SocketTimeoutException]: connect timed out

I am getting a SocketTimeoutException with an AS2 connection (Mendelson to an AS2 server placed in the DMZ. I am looking for two things:
1. How can I increase the log level so I can figure out if the handshake is okay, and what component of the network is causing the timeout.
2. Are there other troubleshooting tools available that can rootcause this issue?

The log entries as available:
1. Outbound message signed with the algorithm "SHA-1", using keystore alias "XXXX".
2. Outbound message encrypted with the algorithm "3DES", using keystore alias "YYYY".
3. Outbound AS2 message created from "TL_20161003.xml" for the receiver "R1" in 240ms, raw message size: 10.14 KB
4. The file "TL_20161003.xml" has been deleted and enqueued into the processing message queue of the server.
5. Sending AS2 message to https://.com/AS2, sync MDN requested.
6. MessageHTTPUploader.performUpload: [SocketException]: Socket Closed
7. Connection problem, failed to transmit data.
8. The max retry has been reached, transmission canceled.