We are developing a DICOM component and for testing we are using DVTK Modality Emulator.

We are using an ECHO test as an initial test. We are noticing that in bytes 3-6 (PDU-length) we are getting 00H 00H 00H 63H in the message as PDU-Length. This means the length is 99. Isn't that right?

But in reality the actual message is 211 bytes long. Shouldn't we recieve CD (Equi. to 205 dec; 211 - 6 = 205) in this field?

Also, what is that the emulator expecting back in this field in ASSOCIATE-AC? We are trying to send the actual length of the data minus 6 in this field but emulator hangs after it recieves that response. If we don't change the value in ASSOCIATE-AC then the emulator fails.
Any pointer/help would be appreciated in this.

We are referring to DICOM manual Part 08 Network Xchange for this field (PDU-length - shall be the number of bytes from the first byte of the following field to the last byte of the variable field. It shall be encoded as an unsigned binary number.)

Thanks,
--Atul

In DICOM, only the actual length of the data is represented by the PDU length.You dont have subtract 6 before sending the data. Try using the DVTk Network Analyzer to sniff the packets and check what the actual length is. A more detailed description of the scenario will help.