EventLoop.registerIo

Token registerIo(Handle handle,  IoInterest interest,  IoWatcherCallback callback,  WatcherFlags extraFlags =  WatcherFlags.none)

@trusted nothrow

When EventLoopConfig.edgeTriggeredDefault is true (the default), the watcher is registered with EPOLLET semantics. The callback must read (or write) until the syscall returns EAGAIN — partial drains will stall the connection because the kernel will not deliver a new event for data already buffered when the callback ran. Use drainToEAGAIN from eve.aio.posix.tcp for HTTP keep-alive style request parsing.

Parameters

`handle`	Native handle to watch.
`interest`	Requested readiness mask.
`callback`	Callback invoked for matching readiness events.

Returns

New watcher token on success, or Token.invalid with errno set.