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Manufacturing · head to head

Kepware Server vs Solace PubSub+

Kepware Server logo

Kepware Server

Manufacturing

Industrial connectivity server translating 150-plus PLC protocols into OPC UA, formerly KEPServerEX

From
On request
Rated
-
Full reviewWebsite
Solace PubSub+ logo

Solace PubSub+

Databases

Multi-protocol event broker sold as software, cloud service or a hardware appliance

From
Free
Rated
-
Full reviewWebsite

The short version

  • Only Solace PubSub+ has a free tier, so it costs nothing to try first.
  • Each has a real cost: Kepware Server the base server is the small part of the bill; driver suites are priced by protocol family, and a mixed-vendor plant buys several, which is how a connectivity layer alone reaches tens of thousands of dollars.; Solace PubSub+ no pricing is published at any tier, so evaluation requires a sales engagement before you can even judge whether it is in budget, and broker tier sizing determines cost in ways buyers frequently get wrong.
  • They diverge on capability: Kepware Server covers 150-plus device drivers, Solace PubSub+ covers Multi-protocol broker.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which Kepware Server and Solace PubSub+ actually diverge.

Attributes where Kepware Server and Solace PubSub+ differ
AttributeKepware ServerSolace PubSub+
Starting priceOn requestFree
Free tierNoYes
PlatformsWindows, LinuxLinux, Docker, Kubernetes, Cloud, Hardware appliance
CategoryManufacturingDatabases

Identical on both: pricing model (quote), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Kepware Server

  • 150-plus device drivers
  • OPC UA server
  • IoT Gateway
  • DataLogger
  • Redundancy Master
  • Security Policies
  • Configuration API
  • Kepware Edge

Only in Solace PubSub+

  • Multi-protocol broker
  • Dynamic message routing
  • Hardware appliance
  • Event Portal
  • Guaranteed delivery
  • Mission Control
  • Topic hierarchies and wildcards
  • Kafka and MQ bridging

What people use each for

The jobs each tool is most often brought in to do.

Kepware Server

  • Feeding a historian from a mixed plant of Allen-Bradley and Siemens PLCs without writing per-protocol driversnot Solace PubSub+
  • Publishing CNC machine state from FANUC and Haas controls to an OEE system over MQTTnot Solace PubSub+
  • Bridging legacy serial Modbus devices into an OPC UA architecture during a phased controller replacementnot Solace PubSub+
  • Running redundant collection servers so a cloud analytics pipeline does not lose data during Windows patchingnot Solace PubSub+

Solace PubSub+

  • A bank building an event mesh across regions where a Java JMS application and an MQTT mobile client must share the same topic spacenot Kepware Server
  • An exchange or trading platform with a latency budget that needs the hardware appliance rather than a software brokernot Kepware Server
  • An airline distributing operational events to ground systems, aircraft and partner APIs over different protocolsnot Kepware Server
  • A manufacturer bridging factory MQTT telemetry into an enterprise Kafka estate without writing translation servicesnot Kepware Server

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Kepware Server

  • The base server is the small part of the bill; driver suites are priced by protocol family, and a mixed-vendor plant buys several, which is how a connectivity layer alone reaches tens of thousands of dollars.
  • KEPServerEX to Kepware Server 7 is a migration rather than an in-place upgrade, and driver entitlements do not always transfer cleanly, so budget for revalidating every channel.
  • The full driver portfolio is Windows-only; the Linux product, Kepware Edge, supports a subset of drivers and is subscription-licensed by tag count, so an edge-first architecture cannot simply reuse the Windows configuration.
  • Three names have been in circulation for the same lineage, and quotes, forum answers and integrator experience still mix KEPServerEX, ThingWorx Kepware Server and Kepware Server, which produces mismatched proposals.
  • It is a translation layer with no storage, contextualisation or visualisation of its own, so it is always an addition to a historian or platform purchase rather than a substitute for one.

Solace PubSub+

  • No pricing is published at any tier, so evaluation requires a sales engagement before you can even judge whether it is in budget, and broker tier sizing determines cost in ways buyers frequently get wrong.
  • The free Standard edition has hard capacity and support limits, which makes it useful for development but means any real deployment triggers a commercial negotiation.
  • The proprietary SMF protocol gives the best performance and feature coverage, so teams that lean on it acquire real switching costs even though open protocols are supported.
  • Operating a self-managed high availability broker pair with disaster recovery is a specialist task, and Solace expertise is scarce in the hiring market compared with Kafka skills.
  • Event Portal and Mission Control are licensed as part of platform packages, so the governance tooling that makes an event mesh manageable is not simply included with the broker.

Pricing, plan by plan

Kepware Server

On request
  • Kepware Server$undefined/year
    • Base server as a perpetual licence with annual maintenance, or subscription
    • Driver suites priced by protocol family and bought separately from the server
    • Advanced plug-ins such as IoT Gateway, DataLogger and Redundancy Master licensed individually

Solace PubSub+

Free
  • Software Event Broker StandardFree
    • Free for production within capacity limits
    • Single node, capped connections and queues
    • No vendor support
  • Solace Cloud$undefined/year
    • Managed brokers in tiers from ENT-250 to ENT-100K
    • Foundation, Accelerate and Scale platform packages
    • Fixed subscription or annual consumption drawdown
  • Software Enterprise self-managed$undefined/year
    • Deploy in your own Kubernetes, VMs or data centre
    • High availability and disaster recovery
    • Support with SLA
  • Hardware appliance$undefined/year
    • Purpose-built appliance with FPGA message offload
    • Deterministic low latency
    • Sold with support contract

Which should you pick?

Choose Kepware Server if

  • You need 150-plus device drivers.
  • You work on Windows, Linux.
  • You also want opc ua server.
Kepware Server review

Choose Solace PubSub+ if

  • You need multi-protocol broker.
  • You want to start without paying.
  • You work on Linux, Docker, Kubernetes, Cloud, Hardware appliance.
  • You also want dynamic message routing.
Solace PubSub+ review

Questions people ask

Is Kepware Server or Solace PubSub+ better?
Neither clearly leads. Kepware Server starts at On request and Solace PubSub+ at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Kepware Server or Solace PubSub+?
Solace PubSub+ has a free tier; the other does not. Paid plans start at On request for Kepware Server and Free for Solace PubSub+.
Does Kepware Server or Solace PubSub+ run on more platforms?
Kepware Server runs on Windows, Linux. Solace PubSub+ runs on Linux, Docker, Kubernetes, Cloud, Hardware appliance.
Can I use Solace PubSub+ for free?
Yes. Solace PubSub+ has a free tier, so you can try it without paying. Kepware Server starts at On request.
What is Kepware Server best used for?
Kepware Server is most often used for feeding a historian from a mixed plant of allen-bradley and siemens plcs without writing per-protocol drivers, publishing cnc machine state from fanuc and haas controls to an oee system over mqtt, bridging legacy serial modbus devices into an opc ua architecture during a phased controller replacement, running redundant collection servers so a cloud analytics pipeline does not lose data during windows patching. Of those, feeding a historian from a mixed plant of allen-bradley and siemens plcs without writing per-protocol drivers and publishing cnc machine state from fanuc and haas controls to an oee system over mqtt are not what Solace PubSub+ is typically brought in for.
What can Kepware Server do that Solace PubSub+ cannot?
Kepware Server covers 150-plus device drivers, OPC UA server, IoT Gateway, DataLogger. Solace PubSub+ covers Multi-protocol broker, Dynamic message routing, Hardware appliance, Event Portal.

Answered from the vendors’ own pages

Kepware Server: Is KEPServerEX discontinued?

The name is. KEPServerEX and ThingWorx Kepware Server have been unified into Kepware Server, currently version 7, and the older names are being retired.

Solace PubSub+: Is there a free version of Solace?

Yes, the Standard edition of the software event broker is free for production within capacity limits, with no vendor support.

Kepware Server: Is a perpetual licence still available?

Yes for the Windows server, with annual maintenance. Kepware Edge on Linux is subscription-only.

Solace PubSub+: Does Solace publish prices?

No. Cloud, software and appliance are all quoted, based on broker tier from ENT-250 to ENT-100K and licensing model.

Kepware Server: What drives the price?

The number and type of driver suites, not the number of tags on the Windows product. Kepware Edge is priced by tag count.

Solace PubSub+: Why buy an appliance in 2026?

Deterministic low latency with message processing offloaded to hardware, which matters in capital markets and little elsewhere.

Kepware Server: Can I evaluate it before buying?

Yes. The runtime works for two hours at a time without a licence, indefinitely, which is enough to prove connectivity but not to run production.

Solace PubSub+: Can it replace Kafka?

Not for log retention and stream reprocessing. It is stronger at multi-protocol routing and guaranteed delivery, and the two are often bridged.

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