Will the retiring of the SMBP protocol also hit WCF Azure relay services?

Rick Siepelinga 25 Reputation points
2026-06-03T11:25:36.4933333+00:00

We are using Azure WCF Relay via the legacy Microsoft.ServiceBus SDK to expose a WCF service over Azure Relay, using NetTcpRelayBinding.

Microsoft recently announced the retirement of older Azure Service Bus SDKs and the SBMP protocol (ports 9350–9354) by 30 September 2026.

However, the announcement also states that “Azure WCF Relay still uses this library, and support for this combination will continue until further notice.”

My concern is specifically around networking behavior for WCF Relay:

  • Does NetTcpRelayBinding still rely on SBMP-related ports (9350–9354) in any scenario?
  • Or does it fall back entirely to outbound HTTPS/TCP over port 443 in modern Azure Relay configurations?

So my question is, are WCF Relay scenarios affected by the SBMP/port retirement, or is this change strictly limited to Service Bus messaging (queues/topics)?

Azure Service Bus
Azure Service Bus

An Azure service that provides cloud messaging as a service and hybrid integration.

Answer accepted by question author
Rakesh Mishra 11,340 Reputation points Microsoft External Staff Moderator
2026-06-03T14:29:37.8066667+00:00

Hi Rick,

To clarify, the retirement of the SBMP (Service Bus Messaging Protocol) scheduled for September 30, 2026, primarily affects the Azure Service Bus SDK libraries (WindowsAzure.ServiceBus, Microsoft.Azure.ServiceBus, and com.microsoft.azure.servicebus).

According to official Microsoft Azure Updates:

"Azure WCF Relay still uses this library, and support of this library in combination with this service will continue until further notice."

What this means for you:

  • No immediate breakage: Your existing WCF Relay endpoints using NetTcpRelayBinding (which rely on SBMP) are not being retired on September 30, 2026. They will continue to function as they currently do.
  • Long-term strategy: While there is no hard cutoff date for WCF Relay's SBMP support, it is still recommended to transition to modern, secure protocols like WebSockets or AMQP over port 443 for new developments. You may explore Azure Relay Hybrid Connections, which are built for modern web standards and offer a more future-proof architecture compared to traditional WCF Relay bindings.

If you have strict firewall requirements that necessitate HTTPS (port 443) traffic, migrating to Hybrid Connections is the recommended path forward. To directly answer your questions:

1. Does NetTcpRelayBinding still rely on SBMP-related ports (9350–9354) in any scenario? Or does it fall back entirely to outbound HTTPS/TCP over port 443?

Yes, NetTcpRelayBinding still relies on TCP ports 9350-9354 by default, but it can fall back to port 443 depending on your application's configuration. This behavior is controlled by the ServiceBusEnvironment.SystemConnectivity.Mode setting.

According to the official Azure Relay documentation:

"The connectivity mode describes the protocol the service uses to communicate with the relay service; either HTTP or TCP. Using the default setting AutoDetect, the service attempts to connect to Azure Relay over TCP if it's available, and HTTP if TCP isn't available." Reference: Expose on-premises WCF REST service to clients

If your mode is set to AutoDetect, the binding will first attempt to use the SBMP ports (9350-9354). If a firewall blocks this outbound traffic, it will gracefully fall back to HTTP over port 443. If you want to bypass the TCP attempt entirely and force 443 from the start, you can change the connectivity mode to HTTP (ConnectivityMode.Http).

2. Are WCF Relay scenarios affected by the SBMP/port retirement, or is this change strictly limited to Service Bus messaging (queues/topics)?

The retirement is strictly limited to Service Bus messaging (queues/topics). Your WCF Relay scenarios are entirely unaffected by the September 30, 2026 deadline.

In short, your existing NetTcpRelayBinding implementations are safe from the 2026 retirement. If you require a strict 443-only outbound topology without the latency of fallback attempts, you can configure your WCF Relay code to use ConnectivityMode.Http, or eventually migrate to Azure Relay Hybrid Connections. Note: This response is drafted with the help of AI systems.

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  1. AI answer

    2026-06-03T11:26:03.48+00:00

    WCF Relay scenarios that use NetTcpRelayBinding are not described as using the SBMP ports (9350–9354). Instead, NetTcpRelayBinding uses its own set of ports.

    From the documented Azure Relay port settings:

    • NetTcpRelayBinding (client/service) uses ports 5671/9352/HTTP (and 9352/9353 if using hybrid).
    • SBMP-related ports 9350–9354 are associated with other WCF Relay bindings (for example, NetEventRelayBinding and NetOnewayRelayBinding use 9350/9351) and with older Service Bus messaging protocols.

    The Service Bus FAQ explicitly calls out the retirement of the older Service Bus SDKs and the SBMP protocol, but this retirement notice is scoped to Azure Service Bus messaging (queues/topics) and the corresponding SDKs (WindowsAzure.ServiceBus, Microsoft.Azure.ServiceBus, com.microsoft.azure.servicebus).

    The available Relay APIs documentation clarifies that:

    • WCF Relay for .NET Framework uses the WindowsAzure.ServiceBus library and a proprietary binary protocol based on the WCF net.tcp transport.
    • This protocol and library are maintained for backward compatibility with existing applications.

    Within the provided information, there is no statement that NetTcpRelayBinding has moved to or “falls back” to HTTPS/port 443, nor that it is directly affected by the SBMP retirement. The SBMP retirement is explicitly tied to Service Bus messaging libraries and protocol, while WCF Relay is described separately and continues to rely on its own port set (including 5671/9352/9353) and the WCF net.tcp-based protocol.

    Therefore, based on the documented port usage and scope of the retirement notice in the context:

    • NetTcpRelayBinding continues to use its documented ports (5671/9352/9353) and is not described as relying on SBMP ports 9350–9354.
    • The SBMP/port retirement is documented as a Service Bus messaging (queues/topics) concern, not as a change to WCF Relay networking behavior.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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