Closes the RawSynchronousSocket.
Once closeSync has been called, attempting to call readSync, readIntoSync, writeFromSync, remoteAddress, and remotePort will cause a SocketException to be thrown.
void closeSync();
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-io/RawSynchronousSocket/closeSync.html