Articles
Technical articles on HL7, MLLP, message validation, and deployment patterns.
What is MLLP and how does it work
MLLP wraps HL7 messages in three framing bytes and sends them over TCP. How the protocol works, why healthcare still uses it, and what to know before implementing it.
HL7 ACK and NAK codes: AA, AR, AE explained
HL7 acknowledgment codes tell the sender what happened to their message. AA means accepted, AR means rejected permanently, AE means try again.
MLLP framing bytes: 0x0B, 0x1C, 0x0D
MLLP uses three bytes to frame HL7 messages over TCP. How start block, end block, and carriage return work together, and the edge cases that break implementations.
CEL expressions for HL7 message validation
Common Expression Language lets you write HL7 validation rules as one-line boolean expressions. Compiled at startup, evaluated per message, mapped to ACK codes.
MLLP vs HTTP for HL7 messaging
MLLP and HTTP both carry HL7 messages but differ in connection model, routing, load balancing, and observability. When to use which, and why the choice is rarely yours.
Choosing an HL7 integration engine in 2026
The HL7 integration landscape shifted when Mirth Connect went closed-source. Here are the options — commercial, open source, cloud, and lightweight — and what each is good at.