RPC_S_CALL_IN_PROGRESS - 1791 (0x6FF)
A remote procedure call is already in progress for this thread.
Updated: Feb 21, 2026
Technical Meaning
The error code RPC_S_CALL_IN_PROGRESS (1791, 0x6FF) is returned when a remote procedure call (RPC) is already in progress for the current thread. This indicates that an attempt to initiate another RPC on the same thread has failed because there is already an active RPC call.
Error Details
This error typically occurs in scenarios where multiple RPC calls are attempted sequentially within the same thread, and only one can be processed at a time due to the nature of asynchronous communication protocols. The operating system ensures that only one RPC call is active per thread to maintain proper synchronization and avoid race conditions.
Usage Context
The RPC_S_CALL_IN_PROGRESS error code is relevant in environments where applications make frequent or concurrent calls to remote procedures over a network. It can be encountered when using the Windows Remote Procedure Call (RPC) API, which is commonly used for inter-process communication across different processes or machines.
Developer Interpretation
When this error is returned, it signifies that the application should not attempt to initiate another RPC call on the same thread until the current one has completed. Developers must ensure that their code handles such scenarios appropriately by managing the sequence of calls and waiting for the completion of ongoing operations before initiating new ones.
Related Errors
RPC_S_CALL_FAILED(1790, 0x6F8): Indicates a failure in an RPC call.RPC_S_CALL_ACTIVE(1792, 0x6FA): Indicates that the RPC call is still active and cannot be canceled.
FAQ
Q: What does the error code RPC_S_CALL_IN_PROGRESS mean?
A: It indicates that a remote procedure call is already in progress for the current thread.
Q: How can I handle this error in my application?
A: Ensure that your application manages the sequence of RPC calls and waits for the completion of ongoing operations before initiating new ones.
Summary
The RPC_S_CALL_IN_PROGRESS error code is a specific technical indicator used by the Windows Remote Procedure Call (RPC) API to prevent concurrent calls on the same thread. Developers should handle this error by managing the sequence of RPC calls and ensuring proper synchronization.