Why is UDP Socket connector timing out? - mule-esb

Question

I am trying to use a UDP socket to send a simple datagram to a local service. I've tested the request and response using a nodejs client, but I cannot get the same response when using Mulesoft.
This is the nodejs code that works:
const dgram = require('node:dgram');
const process = require('node:process');
const buffer = require('node:buffer');
var soc = dgram.createSocket('udp4');
soc.on('error', (err) => {
console.error(`socket error:\n${err.stack}`);
});
soc.on('message', (msg) => {
console.log(`message received: ${msg}`);
});
soc.connect(1434, () => {
console.log(`socket connected`);
const queryInstanceCode = 3;
const buff = buffer.Buffer.alloc(1);
buff[0] = queryInstanceCode;
soc.send(buff);
});
Executing this node app will query the local service and return expected data.
My mule app uses the socket connector with this configuration:
<?xml version="1.0" encoding="UTF-8"?>
<mule xmlns:scripting="http://www.mulesoft.org/schema/mule/scripting" xmlns:sockets="http://www.mulesoft.org/schema/mule/sockets"
xmlns:http="http://www.mulesoft.org/schema/mule/http"
xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
http://www.mulesoft.org/schema/mule/sockets http://www.mulesoft.org/schema/mule/sockets/current/mule-sockets.xsd
http://www.mulesoft.org/schema/mule/scripting http://www.mulesoft.org/schema/mule/scripting/current/mule-scripting.xsd">
<http:listener-config name="HTTP_Listener_config" doc:name="HTTP Listener config" doc:id="aaeb8ad9-c25d-4076-90b4-5fbf0584fefa" >
<http:listener-connection host="0.0.0.0" port="8081" />
</http:listener-config>
<sockets:request-config name="SQLServiceBrowserSocket" doc:name="Sockets Request config" doc:id="ccebf069-3ea5-403b-8f38-14a1b181c93f" >
<sockets:udp-requester-connection host="127.0.0.1" port="1434" clientTimeout="5000"/>
</sockets:request-config>
<flow name="named.instance.finderFlow" doc:id="f0259fdc-c7ce-43ba-a124-07df0bee9ec4" >
<http:listener doc:name="Listener" doc:id="3ece9740-15b6-4681-b5e3-20ff66fa46c7" config-ref="HTTP_Listener_config" path="/mssqlhost/{host}/instance/{instance}/port" allowedMethods="GET" responseStreamingMode="NEVER">
</http:listener>
<logger level="INFO" doc:name="Log Request" doc:id="3bd2076d-23f6-4388-a3d8-0da2816d00dc" message="#attributes"/>
<sockets:send-and-receive doc:name="Query SQL Server Browser" doc:id="14f15af2-ee9a-41f9-9890-a021fd066d35" config-ref="SQLServiceBrowserSocket" target="instancePort" outputMimeType="application/octet-stream" outputEncoding="US-ASCII">
<non-repeatable-stream />
<sockets:content><![CDATA[3]]></sockets:content>
</sockets:send-and-receive>
<logger level="INFO" doc:name="Logger" doc:id="6ca780c0-21c7-409c-9c64-17cb0a0fc543" message="#payload"/>
</flow>
</mule>
When running the Mule app and performing a simple CURL on the url, the flow will timeout after 5 seconds, with no additional information than "UDP connection timed out".
I've tried adding debug logging for sockets, but I get no additional information. How do I get additional information on why the UDP Sockets connector is not properly interacting with the service?
The nodejs application works and proves that the service is available and functioning. The Mule application times out after 5 seconds without any further information. I have tried increasing level logging by adding this logger:
<AsyncLogger name="org.mule.extension.socket" level="DEBUG"/>
To the log4j2.xml of the package, but I get no additional information.
I expect the Sockets connector to send the UDP packate and receive the same response that the nodejs application receives. Instead the Socket connector times out.

Answer 1

The issue was encoding. Supplying the string "3" to the content of the socket made it encoded in ASCII. Instead, use dataweave:
%dw 2.0
output application/octet-stream
---
3