RFC du protocole POP (POP3) : TRANSACTION
5. The TRANSACTION State
Once the client has successfully identified itself to the POP3 server
and the POP3 server has locked and opened the appropriate maildrop,
the POP3 session is now in the TRANSACTION state. The client may now
issue any of the following POP3 commands repeatedly. After each
command, the POP3 server issues a response. Eventually, the client
issues the QUIT command and the POP3 session enters the UPDATE state.
Here are the POP3 commands valid in the TRANSACTION state:
STAT
Arguments: none
Restrictions:
may only be given in the TRANSACTION state
Discussion:
The POP3 server issues a positive response with a line
containing information for the maildrop. This line is
called a "drop listing" for that maildrop.
In order to simplify parsing, all POP3 servers required to
use a certain format for drop listings. The positive
response consists of "+OK" followed by a single space, the
number of messages in the maildrop, a single space, and the
size of the maildrop in octets. This memo makes no
requirement on what follows the maildrop size. Minimal
implementations should just end that line of the response
with a CRLF pair. More advanced implementations may
include other information.
NOTE: This memo STRONGLY discourages implementations
from supplying additional information in the drop
listing. Other, optional, facilities are discussed
later on which permit the client to parse the messages
in the maildrop.
Note that messages marked as deleted are not counted in
either total.
Possible Responses:
+OK nn mm
Examples:
C: STAT
S: +OK 2 320
LIST [msg]
Arguments:
a message-number (optional), which, if present, may NOT
refer to a message marked as deleted
Restrictions:
may only be given in the TRANSACTION state
Discussion:
If an argument was given and the POP3 server issues a
positive response with a line containing information for
that message. This line is called a "scan listing" for
that message.
If no argument was given and the POP3 server issues a
positive response, then the response given is multi-line.
After the initial +OK, for each message in the maildrop,
the POP3 server responds with a line containing information
for that message. This line is also called a "scan
listing" for that message.
In order to simplify parsing, all POP3 servers are required
to use a certain format for scan listings. A scan listing
consists of the message-number of the message, followed by
a single space and the exact size of the message in octets.
This memo makes no requirement on what follows the message
size in the scan listing. Minimal implementations should
just end that line of the response with a CRLF pair. More
advanced implementations may include other information, as
parsed from the message.
NOTE: This memo STRONGLY discourages implementations
from supplying additional information in the scan
listing. Other, optional, facilities are discussed
later on which permit the client to parse the messages
in the maildrop.
Note that messages marked as deleted are not listed.
Possible Responses:
+OK scan listing follows
-ERR no such message
Examples:
C: LIST
S: +OK 2 messages (320 octets)
S: 1 120
S: 2 200
S: .
...
C: LIST 2
S: +OK 2 200
...
C: LIST 3
S: -ERR no such message, only 2 messages in maildrop
RETR msg
Arguments:
a message-number (required) which may not refer to a
message marked as deleted
Restrictions:
may only be given in the TRANSACTION state
Discussion:
If the POP3 server issues a positive response, then the
response given is multi-line. After the initial +OK, the
POP3 server sends the message corresponding to the given
message-number, being careful to byte-stuff the termination
character (as with all multi-line responses).
Possible Responses:
+OK message follows
-ERR no such message
Examples:
C: RETR 1
S: +OK 120 octets
S: <the POP3 server sends the entire message here>
S: .
DELE msg
Arguments:
a message-number (required) which may not refer to a
message marked as deleted
Restrictions:
may only be given in the TRANSACTION state
Discussion:
The POP3 server marks the message as deleted. Any future
reference to the message-number associated with the message
in a POP3 command generates an error. The POP3 server does
not actually delete the message until the POP3 session
enters the UPDATE state.
Possible Responses:
+OK message deleted
-ERR no such message
Examples:
C: DELE 1
S: +OK message 1 deleted
...
C: DELE 2
S: -ERR message 2 already deleted
NOOP
Arguments: none
Restrictions:
may only be given in the TRANSACTION state
Discussion:
The POP3 server does nothing, it merely replies with a
positive response.
Possible Responses:
+OK
Examples:
C: NOOP
S: +OK
RSET
Arguments: none
Restrictions:
may only be given in the TRANSACTION state
Discussion:
If any messages have been marked as deleted by the POP3
server, they are unmarked. The POP3 server then replies
with a positive response.
Possible Responses:
+OK
Examples:
C: RSET
S: +OK maildrop has 2 messages (320 octets)
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