Testing DemoDispatcher with external application

[leonardorame]

Hi, I would like to use elixir-mllp to create an HL7 server, so far I just cloned this repository and created the DemoDispatcher example, then instantiated with:

{:ok, r4090} = MLLP.Receiver.start(port: 4090, dispatcher: DemoDispatcher)

After that, I just send an HL7 file with netcat, this way:

cat test.hl7|nc 127.0.0.1 4090

The contents of this file is:

^KMSH|^~\\&|MegaReg|XYZHospC|SuperOE|XYZImgCtr|20060529090131-0500||ADT^A01^ADT_A01|01052901|P|2.5                                                                                            
EVN||200605290901||||200605290900                                                                                                                                                             
PID|||56782445^^^UAReg^PI||KLEINSAMPLE^BARRY^Q^JR||19620910|M||2028-9^^HL70005^RA99113^^XYZ|260 GOODWIN CREST DRIVE^^BIRMINGHAM^AL^35209^^M~NICKELL’S PICKLES^10000 W 100TH AVE^BIRMINGHAM^AL^
PV1||I|W^389^1^UABH^^^^3||||12345^MORGAN^REX^J^^^MD^0010^UAMC^L||67890^GRAINGER^LUCY^X^^^MD^0010^UAMC^L|MED|||||A0||13579^POTTER^SHERMAN^T^^^MD^0010^UAMC^L|||||||||||||||||||||||||||20060529
OBX|1|N^K&M|^Body Height||1.80|m^Meter^ISO+|||||F                                                                                                                                             
OBX|2|NM|^Body Weight||79|kg^Kilogram^ISO+|||||F                                                                                                                                              
AL1|1||^ASPIRIN                                                                                                                                                                               
DG1|1||786.50^CHEST PAIN, UNSPECIFIED^I9|||A                                                                                                                                                  
^\      

Note: I tried with MLLP envelope (ascii 11 and 28 to wrap) and without it, obtaining the same results.

The Iex console shows this when I send the message:

12:03:05.876 [debug] Receiver received data: [<<11, 77, 83, 72, 124, 94, 126, 92, 92, 38, 124, 77, 101, 103, 97, 82, 101, 103, 124, 88, 89, 90, 72, 111, 115, 112, 67, 124, 83, 117, 112, 101, 114, 79, 69, 124, 88, 89, 90, 73, 109, 103, 67, 116, 114, 124, 50, 48, 48, 54, ...>>].

12:03:05.876 [debug] MLLP.Receiver tcp_closed.

But I don't see the parsed message nor the ACK.

Am I doing anything wrong?

[starbelly]

Hi, first let me say, I hate that you opened this up in August. We are going to start processing this at least weekly going forward.

It looks like from the above that the the trailer is missing (EB followed by CR), but it can be hard to tell from the paste.

 hl7 = <<0x0B>> <> "MSH|^~\\&|MegaReg|XYZHospC|SuperOE|XYZImgCtr|20060529090131-0500||ADT^A01^ADT_A01|01052901|P|2.5\rEVN||200605290901||||200605290900\rPID|||56782445^^^UAReg^PI||KLEINSAMPLE^BARRY^Q^JR||19620910|M||2028-9^^HL70005^RA99113^^XYZ|260 GOODWIN CREST DRIVE^^BIRMINGHAM^AL^35209^^M~NICKELL’S PICKLES^10000 W 100TH AVE^BIRMINGHAM^AL^35200^^O|||||||0105I30001^^^99DEF^AN\rPV1||I|W^389^1^UABH^^^^3||||12345^MORGAN^REX^J^^^MD^0010^UAMC^L||67890^GRAINGER^LUCY^X^^^MD^0010^UAMC^L|MED|||||A0||13579^POTTER^SHERMAN^T^^^MD^0010^UAMC^L|||||||||||||||||||||||||||200605290900\rOBX|1|N^K&M|^Body Height||1.80|m^Meter^ISO+|||||F\rOBX|2|NM|^Body Weight||79|kg^Kilogram^ISO+|||||F\rAL1|1||^ASPIRIN\rDG1|1||786.50^CHEST PAIN, UNSPECIFIED^I9|||A\r" <> <<0x1C>>
File.write!("test.hl7, hl7)

{:ok, r4090} = MLLP.Receiver.start(port: 4090, dispatcher: DemoDispatcher)

cat test.hl7 |nc 127.0.0.1 4090

And it hangs, this is expected though, not all data for the message has been received yet, specifically the receiver has to wait on a carrige return before continuing, as an EB followed by a CR indicates the end of the message. Unfortunately, this is simply the nature of the beast. I'm not sure how we can make this more clear, but perhaps there's room for signaling in the context of the receiver that it is still waiting on data or alternatively, disconnecting a connection after some time goes by without receiving anymore data. Yet it can be hard to come up with reasonable defaults some times. Thoughts are appreciated.

[leonardorame]

Thanks, I wasn't sending the last , after adding it the Receiver went a little further, but it stopped with:

[error] The DefaultPacketFramer is discarding unexpected data:

I'll take a look at it.

[starbelly]

I think what we can do here is add something for debugging, basically an option where after we receive some data, we check every a certain amount of time that we're not still waiting on data, if we are, then we can log a debug message and hang up the phone.

When in doubt about the receiver, I always encourage people to try using our mllp client, which is quite sound and battle tested, to send some data first. In this case it might have helped (assuming you didn't start this way), specifically, it won't even allow invalid hl7 messages through to be sent on to the server.

[bryanhunter]

Hi. Just seeing your message:

it stopped with:
[error] The DefaultPacketFramer is discarding unexpected data:

I think what you are seeing is correct. The unexpected data being discarding is anything outside of the MLLP envelope which started with <<0x0B>> and ended with <<0x1C, 0x0D>>. In your case, I suspect whitespace is coming after your envelope. Maybe a trailing line feed? If you put the word "yuck-garbage" after the <<0x1C, 0x0D>> in your test message you should see an error like:

[error] The DefaultPacketFramer is discarding unexpected data: yuck-garbage

That make sense?

[bryanhunter]

Also, it might help if you create your "test.hl7" file from within Elixir to ensure your text editor isn't messing up the envelope or replacing the HL7 message's "\r" with "\n".

wrapped_hl7 = <<0x1c>> <> "MSH|^~\\&|MegaReg|XYZHospC|SuperOE|XYZImgCtr|20060529090131-0500||ADT^A01^ADT_A01|01052901|P|2.5\rEVN||200605290901||||200605290900\rPID|||56782445^^^UAReg^PI||KLEINSAMPLE^BARRY^Q^JR||19620910|M||2028-9^^HL70005^RA99113^^XYZ|260 GOODWIN CREST DRIVE^^BIRMINGHAM^AL^35209^^M~NICKELL’S PICKLES^10000 W 100TH AVE^BIRMINGHAM^AL^\rPV1||I|W^389^1^UABH^^^^3||||12345^MORGAN^REX^J^^^MD^0010^UAMC^L||67890^GRAINGER^LUCY^X^^^MD^0010^UAMC^L|MED|||||A0||13579^POTTER^SHERMAN^T^^^MD^0010^UAMC^L|||||||||||||||||||||||||||20060529\rOBX|1|N^K&M|^Body Height||1.80|m^Meter^ISO+|||||F\rOBX|2|NM|^Body Weight||79|kg^Kilogram^ISO+|||||F\rDG1|1||786.50^CHEST PAIN, UNSPECIFIED^I9|||A\r" <> <<0x1C, 0x0D>>
File.write("test.hl7", wrapped_hl7)