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Thrown when any of the receive functions are called with a length less than 1. This includes zero and any negative numbers. This indicates misuse of the API and is not considered a recoverable exception.

Requesting a negative number is bytes is clear misuse of the API. But what about zero? This deserves some justification. POSIX allows requesting zero bytes with recv, and the result is that it copies no bytes into the buffer and returns 0. Essentially, it's a no-op. However, the return length 0 is also used to indicate a shutdown. This overloaded meaning of the return value 0 makes it difficult to interpret what it means. (It would be nice if recv instead set the error code to something indicating EOF when the peer had shutdown, but we live in a more difficult world.) To correctly interpret the meaning of return length 0, an application must consider what buffer size it passed to recv. To prevent the caller from having to do this bookkeeping, this library simply forbids requesting 0 bytes with recv. If you do request 0 bytes with recv, you get this exception, and you can fix the part of your program that failed to satisfy the precondition.

This indicates a mistake in this library. Open an issue if this exception is ever thrown.