Fixing Win32 Error 0x000006D1 (RPC_S_PROCNUM_OUT_OF_RANGE)

The error code 0x000006D1 translates to RPC_S_PROCNUM_OUT_OF_RANGE. This error message indicates that the RPC call failed because the client attempted to use a procedure number (procnum) that is not valid for the remote service on the server.

Understanding Procedure Numbers in RPC:

• In RPC communication, each service offered by a server exposes a set of procedures that clients can invoke remotely.
• These procedures are identified by unique numbers (procnums).
• The client includes the procnum in the RPC call to specify the desired operation on the server.
• The RPC_S_PROCNUM_OUT_OF_RANGE error occurs when the client uses a procnum that is not recognized by the server for the specific service being accessed.

Reasons Behind RPC_S_PROCNUM_OUT_OF_RANGE:

There are a couple of reasons why you might encounter this error:

• Incorrect Client Code: The client code might be using an incorrect procnum for the intended operation. This could be due to typos, programming errors, or outdated information.
• Version Mismatch: If the client and server are using different versions of the same service interface, the procnum might have changed between versions, leading to a mismatch.
• Incorrect Service Access (less common): In rare cases, the client code might be attempting to use a procnum meant for a different service altogether.

Resolving RPC_S_PROCNUM_OUT_OF_RANGE:

1. Review Client-Side Code:

   • Examine the part of your client code responsible for making the RPC call. Verify that the procnum being used matches the intended operation for the service.

2. Consult Program Documentation:

   • Refer to the documentation for the program or service you’re trying to access remotely. It should specify the valid procnums for each available procedure.

3. Update Client Software (if applicable):

   • Consider updating the client software to the latest version. This might ensure it uses the correct procnums for the service on the server, especially if versioning is the culprit.

4. Server Administrator Communication (if possible):

   • If possible, communicate with the server administrator to confirm the valid procnums for the service you’re trying to access. This can help identify inconsistencies between client and server expectations.

5. Software Vendor Support:

   • If the issue persists, consider contacting the software vendor’s support for the program or service. They might have insights into compatible procnum usage or troubleshooting steps for their software.

Additional Tips:

• Some RPC development tools or libraries might offer functionalities to browse or validate procnums for specific services.
• Debuggers or logging mechanisms can help capture details about the procnum being used in the RPC call and any error messages related to invalid procnums.

By understanding the concept of procnums in RPC and the reasons behind out-of-range errors, you can identify the cause of the invalid procnum usage. Reviewing client-side code, consulting program documentation, updating client software (if applicable), communicating with the server administrator (if possible), and contacting software vendor support can help address this error.