6.44.3.2 Ports and non-blocking mode

Function: port-set-non-blocking-mode! port

Set non–blocking mode for port; if successful return unspecified values, if an error occurs raise an exception. port must have a file descriptor as underlying device.

Function: port-unset-non-blocking-mode! port

Unset non–blocking mode for port; if successful return unspecified values, if an error occurs raise an exception. port must have a file descriptor as underlying device.

Function: port-in-non-blocking-mode? port

Query port for its non–blocking mode; if successful: return #t if the port is in non–blocking mode, #f otherwise. If an error occurs: raise an exception.

port can be any Scheme port: this function will recognise non-blocking mode only for ports having a file descriptor as underlying device; for all the other ports the return value is #f.