HTTP POST Message Transfers

PHC Hub receives HL7 messages using a protocol defined in the document titled "Transport of Immunization HL7 Transaction over the Internet Using Secure HTTP version 1.0" written by the HL7 Immunization Registry Task Force (Rockmore, Yeatts, and Davidson). It describes sending an HL7 message, a username, a password, and a facility ID in an HTTP POST transaction and receiving an HL7 message as a response.

For an external system to connect to the immunization registry, it must have two features:

• A connection to the internet so that it can "see" the registry's web interface
• The ability to send HL7 immunization messages using HTTPS

Request Encoding

When the sending application sends PHC Hub an HL7 message via an HTTPS POST command, it must have the following fields:

• USERID - Assigned by the PHC Hub administrator
• PASSWORD - Assigned by the PHC Hub administrator
• MESSAGEDATA - The HL7 messages

HL7 messages may be sent one at a time (one for every HTTPS request) or grouped in a batch. Batch messages do not have any special separators or wrappers, but the standard HL7 batch protocol may be used. The batch is formatted as follows:

Response Encoding

PHC Hub returns responses to the sending system. Requests with multiple messages can have multiple responses, one for each request message. Responses are returned as defined in the account configuration. The available options are:

• Always - Always send a response for a message
• Never - Never send a response for a message
• On Error - Send responses only for those messages that have errors and are not accepted
• Determined by Message - Use the incoming message's MSH segment to determine the response option (Always, Never, or Only on Error)

Responses from the HL7 interface are always in HL7 format. HL7 responses can indicate any one of the following:

• Authentication error - The HL7 user making the request is not allowed to because the username and password are incorrect or the account does not have permission to accept HL7 messages
• Message parsing error - The HL7 parser is unable to read the incoming message because it doesn't conform to HL7 standards
• Message content error - PHC Hub cannot accept the data because of missing or incorrect information
• Message processing exception - PHC Hub cannot process the message because of an unexpected problem
• Message accepted - PHC Hub has accepted the data and is either holding it for review or submitting it to the IIS for processing
• Response to query - The IIS responds to the query with query results

Related topics:

• HTTP Upload Message Transfers
• CDC WSDL Message Transfers
• TCP/IP Message Transfers
• Local File Message Transfers
• FTP Server