Websockets

WebSocket

Authentication & Connection Flow

Before you can receive the WebSocket data stream, the connection must be authenticated with a session cookie obtained from the HTTP login endpoint.

1. Obtain a session cookie

Send a POST request to the PDU’s login endpoint with valid credentials.

Example (cURL)

Bash

curl -i \
  -X POST "http://<PDU_IP>/api/login" \
  -H "Content-Type: application/json" \
  -d '{
    "username": "<USERNAME>",
    "password": "<PASSWORD>"
  }'

Look for the Set-Cookie header in the response:

HTTP

Set-Cookie: SPID=23zc7Eloswmdt7ofjc; Path=/; HttpOnly

Save the cookie string.

2. Open the WebSocket connection

ws://<PDU_IP>/ws

3. Authenticate by sending cookie

JSON

{"cookie": "SPID=23zc7Eloswmdt7ofjc"}

Example Browser Flow

JavaScript

async function connectToPdu(ip, username, password) {
  await fetch(`http://${ip}/api/login`, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ username, password }),
    credentials: "include"
  });

  const ws = new WebSocket(`ws://${ip}/ws`);

  ws.onopen = () => {
    ws.send(JSON.stringify({ cookie: document.cookie }));
  };

  ws.onmessage = (event) => {
    console.log("Data:", JSON.parse(event.data));
  };
}

WebSocket Data Stream

When successfully connected AND authenticated. SynLink PDU's will output a data stream onto a WebSocket with the following WebSocket Data Stream Object at a rate of once every 2 seconds.

WebSocket Data Stream Object

Key	Type	Description
device	object	Object with uptime and time
banks	array	Array of WebSocket Bank Object(s)
inlets	array	Array of WebSocket Inlet Object(s)
outlets	array	Array of WebSocket Outlet Objects if applicable
sensors	array	Array of Sensor Outlet Object(s) if connected

WebSocket Device Object

Key	Type	Description
uptime	number	Number of seconds the PDU has been on.
time	string	Time in ISO8601 String Format.

WebSocket Bank Object

Key	Type	Description
id	string	Unique identifier for the bank
currentRms	number	The instantaneous current measured at the inlet in Amps
voltageRms	number	Instantaneous voltage reading at inlet and all outlets in volts
lineFrequency	number	Line Frequency measurement valid from 45-65 GHz
powerFactor	number	Power Factor reading. Value is signed value representing polarity of power factor
activePower	number	Active Power measured in KW (kiloWatts). Power consumed by electrical resistance
apparentPower	number	Power which is actually consumed or utilized
energyAccumulation	number	Number of kilowatt hours accumulated. Can be used as billing unit for energy delivered
hasCircuitBreakerProtection	boolean	true if PDU has circuit breaker protection.
circuitBreakerClosed	boolean	State of circuit breakers. true if circuit breaker is closed and providing power correctly.

WebSocket Inlet Object

Key	Type	Description
id	string	Unique identifier for Inlet
inletType	string	Describes configuration of specific Inlet Object. Either "single", "dual", or "ats".
inletPlug	string	Connector type for Inlet
inletName	string	User defined name for inlet
inletEnergyAccumulation	number	kWH value to show energy consumption for inlet plug. If multiple inlets, value will stay same for all inlets.

Conditional WebSocket Inlet Object Attributes

Is available when PDU is a three phase PDU

Key	Type	Description
inletPowerFactor	number	Power factor value for inlet plug
threePhaseBalance	string	Percentage unbalance for 3 phase circuit
inletLines	array	Contains 3 line objects, each with "currentRMS" in amps, unique "id", and "line" it is associated with.

Is available when PDU is a single phase PDU

Key	Type	Description
inletCurrentRms	number	Inlet current draw in amps
inletVoltageRms	number	Inlet voltage RMS in volts
inletLineFrequency	number	Inlet line frequency in hertz
inletPowerFactor	number	Power factor ratio
inletActivePower	number	Inlet Active Power in watts
inletApparentPower	number	Inlet Apparent Power in Volt-amperes (VA)
inletLineConfiguration	string	Line configuration for outlets connected to this inlet.

Is available when PDU is an ATS PDU

Key	Type	Description
atsInletId	string	Either "A" or "B". Matches label on PDU.
atsInletActive	boolean	true if inlet is used to power outlets.
atsInletReady	boolean	true if inlet has voltage potential

Data Stream Object

JSON

{
  "device": {
    "uptime": 251362,
    "time": "2012-01-03T22:34Z"
  },
  "banks": [
    {
      "id": 16777225,
      "currentRms": 0.007400000002235174,
      "voltageRms": 117.0999984741211,
      "lineFrequency": 60.1879997253418,
      "powerFactor": -0.465087890625,
      "activePower": 0.4000000059604645,
      "apparentPower": 0.8600000143051147,
      "hasCircuitBreakerProtection": false,
      "circuitBreakerClosed": true,
      "energyAccumulation": 0
    },
    ...
  ],
  "inlets": [
    {
      "id": "I1-9826498",
      "inletCurrentRms": 0.007400000002235174,
      "inletVoltageRms": 117.0999984741211,
      "inletLineFrequency": 60.1879997253418,
      "inletPowerFactor": 0.4651162922382355,
      "inletActivePower": 0.4000000059604645,
      "inletApparentPower": 0.8600000143051147,
      "inletEnergyAccumulation": 0
    }
  ],
  "outlets": [
    {
      "id": "1-16777225",
      "currentRms": 0.16098617017269135,
      "state": "ON",
      "voltageDetection": true,
      "relayHealth": "OK"
    },
    ...
  ],
  "sensors": [
    {
      "sensorPort": "B",
      "sensorName": "Temperature & Humidity Sensor",
      "sensorTempInC": 18.23232650756836,
      "sensorTempInF": 64.81819152832031,
      "sensorHumidity": 59.186912536621094,
      "sensorType": "temp_hum"
    },
    ...
  ]
}