Fixing Win32 Error 0x000006B7 (RPC_S_NO_PROTSEQS)

The error code 0x000006B7 translates to RPC_S_NO_PROTSEQS. This error message indicates that the RPC system couldn’t find any available protocol sequences that are compatible with both the client and server for the RPC connection.

Understanding Missing Compatible Protocol Sequences:

• In RPC communication, protocol sequences define how data is packaged and transmitted between client and server.
• The RPC system attempts to negotiate a mutually supported protocol sequence during connection establishment.
• The RPC_S_NO_PROTSEQS error occurs when no common protocol sequence is found that both the client and server can use for the RPC connection.

Reasons Behind RPC_S_NO_PROTSEQS:

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

• Incompatible Protocol Stacks: The client and server might have different protocol stacks configured, lacking any overlapping support for common RPC protocols.
• Disabled or Missing Protocol Sequences: Essential protocol sequences required for RPC communication might be disabled or missing on either the client or server machine.
• Outdated Client-Side Configuration (rare): In rare cases, outdated client-side configuration might not reflect the available protocol sequences on the server.

Resolving RPC_S_NO_PROTSEQS:

1. Verify Client and Server Protocol Support:

   • Investigate the supported protocol sequences on both the client and server machines. This might involve consulting system documentation or using tools to identify available protocols.

2. Software Vendor Support:

   • If you’re unsure about the supported protocols or encounter issues related to server configuration, consider reaching out to the software vendor’s support for the program or service you’re trying to access remotely. They can provide guidance on compatible protocol sequences for that specific service.

3. Configure Compatible Protocols (if applicable):

   • If possible, try to configure both the client and server to enable common RPC protocol sequences like ncacn_ip_tcp or others supported by both systems.

4. Update Client-Side Configuration (if applicable):

   • In rare cases, update the client-side configuration to reflect the latest available protocol sequences on the server (if applicable). This might involve regenerating client-side stubs or updating configuration files.

5. Review Firewall Rules (if applicable):

   • In some cases, firewall rules might be blocking specific RPC protocol traffic. Ensure firewalls on both client and server allow communication on the necessary ports used by the chosen protocol sequence.

Additional Tips:

• Some RPC development tools might offer features to help with protocol sequence negotiation during connection setup. These tools can suggest compatible protocols based on system capabilities.
• If managing the client or server configuration, ensure both systems have a common set of enabled RPC protocol sequences to facilitate communication.

By understanding the role of protocol sequences in RPC and the reasons behind the RPC_S_NO_PROTSEQS error, you can identify the cause of the missing compatible protocol sequence. Verifying client and server protocol support, contacting software vendor support, configuring compatible protocols (if applicable), updating client-side configuration (if applicable), reviewing firewall rules (if applicable), and maintaining compatible RPC protocol configurations on both client and server can help address this error.