Knowledge

WSAEMSGSIZE - 10040 (0x2738)

A message sent on a datagram socket was larger than the internal message buffer or some other network limit, or the buffer used to receive a datagram into was smaller than the datagram itself.

Updated: Feb 21, 2026

Technical Background

The WSAEMSGSIZE error code is a specific error that occurs in the Windows Sockets API when attempting to send or receive data on a datagram socket. This error indicates that the message being sent exceeds the internal buffer size limit, either due to the sending buffer being too small or the receiving buffer not being large enough to accommodate the incoming message.

Error Details

The WSAEMSGSIZE error code is returned with the numeric value 10040 and the hexadecimal representation 0x2738. This error typically arises in scenarios where the size of a datagram exceeds the maximum allowed by the underlying network protocol or the buffer allocated for handling such messages.

Common Causes

  • Exceeding Maximum Message Size: The message being sent is larger than the maximum allowable size as defined by the network protocol or the system configuration.
  • Insufficient Buffer Allocation: The buffer used to send or receive the datagram is smaller than the actual size of the data being transmitted, leading to a buffer overflow condition.

Real-World Context

Datagram sockets are commonly used in applications that require reliable and ordered delivery of messages. However, these sockets have inherent limitations on message size due to network protocols such as UDP (User Datagram Protocol). When an application attempts to send or receive data that exceeds these limits, the WSAEMSGSIZE error is generated.

Is This Error Critical?

The criticality of this error depends on the specific context in which it occurs. In most cases, it indicates a design limitation rather than a severe system failure. However, if such errors are frequent or occur under normal operating conditions, they may indicate issues with the application's data handling logic.

How to Diagnose

To diagnose WSAEMSGSIZE errors, follow these steps:

  1. Review Operation Context: Ensure that the operation context is correct and consistent with expected usage patterns.
  2. Validate Parameters: Check the parameters passed to socket operations for correctness and compliance with size limits.
  3. Confirm Object Types: Verify that the datagram being sent or received is of the appropriate type and does not exceed the maximum allowed size.
  4. Verify Input Data: Ensure that the input data being transmitted is within acceptable size constraints.
  5. Check Limits or Constraints: Confirm that system limits, such as buffer sizes, are set appropriately to handle the expected message sizes.

How to Resolve

To resolve WSAEMSGSIZE errors, consider these practical steps:

  1. Correct Parameter Usage: Adjust the parameters passed to socket operations to ensure they comply with size limitations.
  2. Adjust Operation Context: Modify the application's operation context if necessary to handle larger messages or adjust buffer sizes accordingly.
  3. Restore Data: If data corruption is suspected, restore the data from a backup or source of truth.
  4. Retry Operation with Valid Inputs: Attempt to send or receive the message again using valid input parameters and buffers.

Developer Notes

Developers should be aware that WSAEMSGSIZE errors can occur due to various factors, including incorrect buffer sizes, oversized messages, or misconfigured network protocols. Ensuring proper validation of data and adherence to size constraints is crucial for maintaining reliable communication in applications using datagram sockets.

Related Errors

  • WSAEWOULDBLOCK: Indicates that a non-blocking socket operation would have blocked if the operation had been blocking.
  • WSAENOSPC: Indicates insufficient space on the device, which could be related to buffer allocation issues.
  • WSAEINVAL: Indicates an invalid argument passed to a function, possibly due to incorrect parameter values or sizes.

FAQ

Q: What does WSAEMSGSIZE mean?

A: WSAEMSGSIZE indicates that the message being sent on a datagram socket exceeds the internal buffer size limit or network protocol constraints.

Q: How can I prevent this error from occurring?

A: Ensure that your application correctly validates and handles data sizes, adheres to buffer limits, and uses appropriate parameters for socket operations.

Q: Can this error be critical in certain scenarios?

A: While generally not a severe issue, frequent or unexpected WSAEMSGSIZE errors may indicate underlying problems with the application's design or configuration.

Summary

The WSAEMSGSIZE error code is specific to datagram socket operations and indicates that messages are too large for the current buffer settings. By understanding its causes and implementing appropriate diagnostic and resolution strategies, developers can ensure reliable communication in their applications.