src/Pure/System/system_channel.ML
2013-01-10 ago recovered buffered sockets from 11f622794ad6 -- requires Poly/ML 5.5.x;
2011-10-17 ago always use sockets on Windows/Cygwin;
2011-09-23 ago raw unbuffered socket IO, which bypasses the fragile BinIO layer in Poly/ML 5.4.x;
2011-09-22 ago abstract System_Channel in ML (cf. Scala version);