OCPP proxy vs gateway vs broker: what each one does

A charger that speaks OCPP holds one connection to one back office, its CSMS. As soon as you want something between the two, three words come up: proxy, gateway and broker. They are used loosely, and what a German searcher calls an "OCPP-Broker" is often what an English one calls an OCPP proxy.

Plugchoice runs a free OCPP proxy. We use the three words like this. A proxy relays one charger connection to several back offices. A gateway connects devices that cannot reach a back office on their own. A broker distributes messages, and in many markets the word means a proxy.

What an OCPP proxy does

The charger connects to the proxy as if it were its back office. The proxy opens a connection to each back office as if it were the charger, and relays OCPP messages both ways. The charger is configured once, with the proxy's address, and which back offices receive its traffic is decided in software. What is an OCPP proxy explains the model in full.

A proxy has to settle two questions that a direct connection never asks. Which back office may authorise cards and start sessions? And what happens to the messages while one back office is offline? On Plugchoice, each back office gets a role: Billing decides who may charge, Data and control reads everything and can send commands but never starts or stops a session. Messages for a back office that is offline are held and replayed when it reconnects, and every message is logged.

You need a proxy when:

• one charger needs several back offices, for example a billing party and an energy platform;
• you want to change back office without a site visit;
• you want to try a new platform on a few chargers before moving the rest.

What an OCPP gateway does

A gateway sits where a device cannot talk to the back office by itself, and it changes what is sent. It comes in three common forms:

• Protocol translation. A device that speaks Modbus or a maker's own protocol is presented to the back office as an OCPP charger.
• Version translation. The charger speaks one OCPP version and the back office another, and the gateway converts between them.
• Site gateway. The chargers of one site connect to a local controller, and the controller holds one connection to the back office.

You need a gateway when your hardware does not speak the protocol or version of your back office, or when a site with many chargers has one network uplink. A gateway does not give a charger a second back office; that is the job of a proxy.

What an OCPP broker does

The word comes from messaging, where a broker receives messages and hands them to everyone who subscribed. Applied to OCPP, it means software that distributes a charger's messages over several back offices, often with rules for which party receives which message. In German-speaking markets "OCPP-Broker" is the usual word for an OCPP proxy.

You need a broker in the same cases as a proxy. Whatever the product is called, ask three questions: which party may start a session, what happens while one back office is offline, and which messages are changed on the way.

Side by side

Where Plugchoice fits

Plugchoice is an OCPP proxy and a free back office in one. The charger connects to wss://ocpp.plugchoice.com, Plugchoice is always one of its back offices, and you add others in the portal or the app, each with the Billing or the Data and control role. The proxy rewrites only message IDs and OCPP 1.6 transaction IDs, and passes signed meter values on as the charger sent them.

Plugchoice is not a gateway. It connects chargers over OCPP 1.6J, depending on model, firmware and configuration, and does not translate other charger protocols. OCPP 2.0.1 and 2.1 are not supported today. The OCPP 1.6J guide lists the messages involved.

To put a second back office on a charger, start at the OCPP proxy page.

Sources

• Open Charge Alliance, the organisation behind OCPP
• Plugchoice OCPP proxy