Implement a HL7 Server Listener¶

This guide explains how to implement a HL7 server listener using the WSO2 Open Healthcare. The HL7 server listener listens for HL7 messages on a specified port and processes the messages. The HL7 server listener is a key component in the healthcare integration process, as it allows you to receive HL7 messages from external systems and process them according to your requirements.

:::note These guides use Ballerina, a language designed for integration and network services, to build healthcare integrations as microservices. :::

Ballerina¶

The following example demonstrates how to implement a HL7 server listener using Ballerina. The example defines a HL7 server listener that listens for HL7 messages on a specified port and processes the messages.

Step 1: Set Up Ballerina¶

Before you begin, ensure you have Ballerina installed on your system.

Step 2: Implement the HL7 server listener¶

Create a Ballerina project using the following command. It will create the Ballerina project and the main.bal file can be used to implement the logic.
```
$ bal new hl7_server_listener_sample
```

Import the required modules to the Ballerina program and implement the logic to create a HL7 server listener. In this sample, we are using the HL7v2.3 version. Therefore, we need to import the ballerinax/health.hl7v23 package. If you are using a different version of HL7, you can import the relevant package. Then the HL7 server listener is created and started to listen for HL7 messages on the specified port.

import ballerina/io;
import ballerina/tcp;
import ballerinax/health.hl7v2;
import ballerinax/health.hl7v23;

service on new tcp:Listener(3000) {
    remote function onConnect(tcp:Caller caller) returns tcp:ConnectionService {
        io:println("Client connected to HL7 server: ", caller.remotePort.toString());
        return new HL7ServiceConnectionService();
    }
}

service class HL7ServiceConnectionService {
    *tcp:ConnectionService;

    remote function onBytes(tcp:Caller caller, readonly & byte[] data) returns tcp:Error? {
        string|error fromBytes = string:fromBytes(data);
        if fromBytes is string {
            io:println("Received HL7 Message: ", fromBytes);
        }

        // Note: When you know the message type you can directly get it parsed.
        hl7v23:ADT_A01|error parsedMsg = hl7v2:parse(data).ensureType(hl7v23:ADT_A01);
        if parsedMsg is error {
            return error(string `Error occurred while parsing the received message: ${parsedMsg.message()}`, 
            parsedMsg);
        }
        io:println(string `Parsed HL7 message: ${parsedMsg.toJsonString()}`);
    }

    remote function onError(tcp:Error err) {
        io:println(string `An error occurred while receiving HL7 message: ${err.message()}. Stack trace: `, 
        err.stackTrace());
    }

    remote function onClose() {
        io:println("Client left");
    }
}

Run the Ballerina program using the following command.
```
$ bal run
```