Copyright (c) 2003 Regents of The University of Michigan.
All Rights Reserved.  See COPYRIGHT.

Response codes of x0x are for general commands, e.g. QUIT, NOOP.  x3x
are for STAT, x4x are for RETR, x5x for STOR.

BANNER

QUIT causes the server to close the connection.

    C:	QUIT "\r\n"
    S:	201 QUIT OK, closing connection "\r\n"

NOOP does nothing, but should generate a valid response.

    C:	NOOP "\r\n"
    S:	202 NOOP OK "\r\n"

All of STAT, RETR, and STOR take similar arguments.

	<path-description> ::=	"COMMAND"			|
				"COMMAND" <command-name>	|
				"TRANSCRIPT" <transcript-name>	|
				"SPECIAL" <path>		|
				"FILE" <transcript-name> <path>

	<path> ::=		encoded ascii blah blah blah

STAT does not allow a "FILE" <path-description>.

    C: STAT <path-description> "\r\n"
    S: 230 Returning STAT information "\r\n"
    S: f <path> <mode> <uid> <gid> <modified-time> <size> <checksum> "\r\n"

RETR

    C: RETR <path-decription> "\r\n"
    S: 240 Retrieving file "\r\n"
    S: <size> "\r\n"
    S: <size bytes of file data>
    S: ".\r\n"

STOR

    C: STOR <path-decription> "\r\n"
    S: 350 Storing file "\r\n"
    C: <size> "\r\n"
    C: <size bytes of file data>
    C: ".\r\n"
    S: 250 File stored "\r\n"

AUTH works per rfc2222 SASL.

COMPress

    C: COMP <compression> [optional-data] "\r\n"
    S: 320 Ready to start "\r\n"
    S: 220 <compression> compression [optional-string] enabled "\r\n"