Association failed: Unrecognized PDU type: 16

Hi Orthanc Community,

We are trying to set up a DICOM listener using Orthanc. I have the Orthanc server running in a docker container. I started another Orthanc instance in my local machine and I can Echo and move data to the remote from my local machine. However, when I try sending data or testing connection from our scanner machine (Siemens Prisma VE11C / Windows with Siemens Syngo version VE11C) I get (with --verbose):

E0501 18:03:54.746535 CommandDispatcher.cpp:468] Receiving Association failed: Unrecognized PDU type: 16

If it helps, the scanner can successfully communicate to an Osirix server (which we are hoping to replace).

Any ideas of what can be happening?

Thank you in advance!


Please check out the troubleshooting guide:

The errors of the family “Receiving Association failed: Unrecognized PDU type” indicate a low-level problem on the network connection. The most common causes are using an encrypted connection (which Orthanc does not support as of release 1.5.6), or trying to connect using a completely different protocol than DICOM (such as DICOMweb).

Make sure that your Siemens modality has DICOM TLS encryption turned off, and that it is not using DICOMweb.

If you want to use DICOMweb, you must install the dedicated Orthanc plugin (, then replace in the Siemens configuration the DICOM port of Orthanc (default: 4242) by the HTTP port of Orthanc (default: 8042).