POP3 stuff, particularly a streaming downloader and a simple command line which runs it.
Project description
POP3 stuff, particularly a streaming downloader and a simple command line which runs it.
Latest release 20210407.2: Provide "pop3" console_script.
I spend some time on a geostationary satellite connection, where round trip ping times are over 600ms when things are good.
My mail setup involves fetching messages from my inbox
for local storage in my laptop, usually using POP3.
The common standalone tools for this are fetchmail
and getmail
.
However, both are very subject to the link latency,
in that they request a message, collect it, issue a delete, then repeat.
On a satellite link that incurs a cost of over a second per message,
making catch up after a period offline a many minutes long exercise in tedium.
This module does something I've been meaning to do for literally years:
a bulk fetch. It issues RETR
ieves for every message up front as fast as possible.
A separate thread collects the messages as they are delivered
and issues DELE
tes for the saved messages as soon as each is saved.
This results in a fetch process which is orders of magnitude faster. Even on a low latency link the throughput is much faster; on the satellite it is gobsmackingly faster.
Class ConnectionSpec(ConnectionSpec,builtins.tuple)
A specification for a POP3 connection.
Method ConnectionSpec.connect(self)
Connect according to this ConnectionSpec
, return the socket
.
Method ConnectionSpec.from_spec(spec)
Construct an instance from a connection spec string
of the form [tcp:
|ssl:
][user@
][tcp_host!]server_hostname[:
port].
The optional prefixes tcp:
and ssl:
indicate that the connection
should be cleartext or SSL/TLS respectively.
The default is SSL/TLS.
Property ConnectionSpec.netrc_entry
The default NetrcEntry
for this ConnectionSpec
.
Property ConnectionSpec.password
The password for this connection, obtained from the .netrc
file
via the key user@
host:
port.
Class NetrcEntry(NetrcEntry,builtins.tuple)
A namedtuple
representation of a netrc
entry.
Method NetrcEntry.by_account(account_name, netrc_hosts=None)
Look up an entry by the account
field value.
Method NetrcEntry.get(machine, netrc_hosts=None)
Look up an entry by the machine
field value.
Class POP3(cs.resources.MultiOpenMixin)
Simple POP3 class with support for streaming use.
Method POP3.client_auth(self, user, password)
Perform a client authentication.
Method POP3.client_begin(self)
Read the opening server response.
Method POP3.client_bg(self, rq_line, is_multiline=False, notify=None)
Dispatch a request rq_line
in the background.
Return a Result
to collect the request result.
Parameters:
rq_line
: POP3 request text, without any terminating CRLFis_multiline
: true if a multiline response is expected, defaultFalse
notify
: a optional handler forResult.notify
, applied if notNone
Note: DOES NOT flush the send stream.
Call self.flush()
when a batch of requests has been submitted,
before trying to collect the Result
s.
The Result
will receive [etc,lines]
on success
where:
etc
is the trailing portion of an ok response linelines
is a list of unstuffed text lines from the response ifis_multiline
is true,None
otherwise TheResult
gets a list instead of a tuple so that a handler may clear it in order to release memory.
Example:
R = self.client_bg(f'RETR {msg_n}', is_multiline=True, notify=notify)
Method POP3.client_dele_bg(self, msg_n)
Queue a delete request for message msg_n
,
return Result
for collection.
Method POP3.client_quit_bg(self)
Queue a QUIT request.
return Result
for collection.
Method POP3.client_retr_bg(self, msg_n, notify=None)
Queue a retrieve request for message msg_n
,
return Result
for collection.
If notify
is not None
, apply it to the Result
.
Method POP3.client_uidl(self)
Return a mapping of message number to message UID string.
Method POP3.dl_bg(self, msg_n, maildir, deleRs)
Download message msg_n
to Maildir maildir
.
Return the Result
for the RETR
request.
After a successful save,
queue a DELE
for the message
and add its Result
to deleRs
.
Method POP3.flush(self)
Flush the send stream.
Method POP3.get_multiline(self)
Generator yielding unstuffed lines from a multiline response.
Method POP3.get_ok(self)
Read server response, require it to be 'OK+'
.
Returns the etc
part.
Method POP3.get_response(self)
Read a server response.
Return (ok,status,etc)
where ok
is true if status
is '+OK'
, false otherwise;
status
is the status word
and etc
is the following text.
Method POP3.readline(self)
Read a CRLF terminated line from self.recvf
.
Return the text preceeding the CRLF.
Return None
at EOF.
Method POP3.readlines(self)
Generator yielding lines from self.recf
.
Method POP3.sendline(self, line, do_flush=False)
Send a line (excluding its terminating CRLF).
If do_flush
is true (default False
)
also flush the sending stream.
Method POP3.shutdown(*a, **kw)
Quit and disconnect.
Method POP3.startup(*a, **kw)
Connect to the server and log in.
Class POP3Command(cs.cmdutils.BaseCommand)
Command line implementation for POP3 operations.
Credentials are obtained via the `.netrc` file presently.
Connection specifications consist of an optional leading mode prefix
followed by a netrc(5) account name
or an explicit connection specification
from which to derive:
* `user`: the user name to log in as
* `tcp_host`: the hostname to which to establish a TCP connection
* `port`: the TCP port to connect on, default 995 for TLS/SSL or 110 for cleartext
* `sni_host`: the TLS/SSL SNI server name, which may be different from the `tcp_host`
The optional mode prefix is one of:
* `ssl:`: use TLS/SSL - this is the default
* `tcp:`: use cleartext - this is useful for ssh port forwards
to some not-publicly-exposed clear text POP service;
in particular streaming performs better this way,
I think because the Python SSL layer does not buffer writes
Example connection specifications:
* `username@mail.example.com`:
use TLS/SSL to connect to the POP3S service at `mail.example.com`,
logging in as `username`
* `mail.example.com`:
use TLS/SSL to connect to the POP3S service at `mail.example.com`,
logging in with the same login as the local effective user
* `tcp:username@localhost:1110`:
use cleartext to connect to `localhost:1110`,
typically an ssh port forward to a remote private cleartext POP service,
logging in as `username`
* `username@localhost!mail.example.com:1995`:
use cleartext to connect to `localhost:1995`,
usually an ssh port forward to a remote private TLS/SSL POP service,
logging in as `username` and passing `mail.exampl.com`
as the TLS/SSL server name indication
(which allows certificate verification to proceed correctly)
Note that the specification may also be a `netrc` account name.
If the specification matches such an account name
then values are derived from the `netrc` entry.
The entry's `machine` name becomes the TCP connection specification,
the entry's `login` provides a default for the username,
the entry's `account` host part provides the `sni_host`.
Example `netrc` entry:
machine username@localhost:1110
account username@mail.example.com
password ************
Such an entry allows you to use the specification `tcp:username@mail.example.com`
and obtain the remaining detail via the `netrc` entry.
Command line usage:
Usage: pop3 subcommand [...]
Subcommands:
dl [{ssl,tcp}:]{netrc_account|[user@]host[!sni_name][:port]} maildir
help [subcommand-names...]
Print the help for the named subcommands,
or for all subcommands if no names are specified.
Method POP3Command.cmd_dl(argv)
Collect messages from a POP3 server and deliver to a Maildir.
Usage: {cmd} [{{ssl,tcp}}:]{{netrc_account|[user@]host[!sni_name][:port]}} maildir
Release Log
Release 20210407.2: Provide "pop3" console_script.
Release 20210407.1: Bump for cs.cmdutils minor bugfix, also fix a few docstring typos.
Release 20210407: Initial PyPI release.
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