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PatternEvent message notifies other applications about something that happened. Unlike document message, the focus is on the timing of the message rather than the content.
How Ballerina helps

Ballerina packages such as HTTP, Kafka, Websocket, etc., in the Ballerina library provide listeners, through which you can consume events from other applications. Each such package provides protocol-specific message sending APIs as well.

Event MessageCommand MessagePoint-to-Point Channel
import ballerina/http;
import ballerina/mime;
import ballerina/url;

type IncidentRequest record {
    string phoneNo;
    Incident incident;

type Incident record {|
    string description;
    string date;
    string time;

const FROM_NO = "+15005550006";
const API_VERSION = "2010-04-01";
const TWILIO_SID = "VBC1849a56d52g41s4b2b2cc004c0027aa8";

final http:Client twilio = check new ("");

service /api/v1 on new http:Listener(8080) {
    resource function post incidents(IncidentRequest req) returns error? {
        string body = string `Incident ${req.incident.description} reported: 
                              ${} at ${req.incident.time}.`;
        http:Request twilioReq = new;
        string payload = "From=" + check url:encode(FROM_NO, "utf-8") +
                         "&To=" + check url:encode(req.phoneNo, "utf-8") +
                         "&Body=" + check url:encode(body, "utf-8");
        twilioReq.setTextPayload(payload, contentType = mime:APPLICATION_FORM_URLENCODED);
        _ = check twilio->/[API_VERSION]/Accounts/[TWILIO_SID]/Messages\,
            targetType = http:Response