The smphone channel is the active (or master) component of the SMTP-over-PhoneNet protocol package. The passive component is the smslave program (see smslave(8)). Smphone establishes a connection to a remote machine's smslave by following the instructions contained in a dialing script. The dialing script is specified in the channel's definition in the runtime tailoring file by the scr= parameter. Scripts reside, by default, in the table directory. See script(5) for information about how to construct a dialing script.
Once a connection has been established, the ``start'' command initiates the PhoneNet link-level (dial) protocol. Several dial package parameters are set by commands in the dialing script. The default illegal character sets are typically compiled into conf_dial.c but those defaults may be overridden by using the DBADIN, DBADOUT, or DBAD specifications in the runtime tailoring file (see section 3.13 of the ``Installing and Operating MMDF II'' document). The defaults may be further superseded by specifying replacement illegal character sets in the dialing script. The dial package defaults to a packet window size of 1. It is the master's responsibility to override that default if desired (see the ``window'' command documented in script(5)).
Smphone is a two-way channel; mail queued on the local machine is delivered to the remote machine and mail queued on the remote machine is picked up. If deliver is called on a smphone channel and mail is queued for that channel, a connection is attempted immediately. If no messages are waiting, then deliver decides whether to invoke the channel to do a pickup of mail from the remote machine. Such a pickup is called a "poll". Deliver looks at the value of the poll= parameter in the smphone channel's runtime tailoring file definition to decide whether to initiate a poll. If the value of poll is 0, polls are never performed. If the value is -1, polls are always performed. Otherwise, the value of poll represents the number of 15-minute intervals to wait before doing a poll. For example, if poll=3 and no messages are queued to be sent out, then any deliver's attempted within 45 minutes of the last successful pickup will return immediately without attempting connection to the remote machine.
The SMTP-over-PhoneNet system uses the dial package as the transport level for sending and receiving messages with standard SMTP (see RFC821). The only addition to conventional SMTP's is that the TURN command is implemented. Smphone first acts as the SMTP sender, sending any queued mail to the remote machine. Then it sends the TURN command and switches to the ``smtpsrvr'' role, accepting mail from the remote machine. When it receives a QUIT command from the remote machine indicating that all messages have been picked up, smphone resumes processing the dialing script on the line following the ``start'' command.
When acting as the ``smtpsrvr'', smphone passes messages to the local submit program which queues messages on the local machine. The source channel and host are set according to the values defined for the specified pobox channel.
S: 220 Server SMTP (Complaints/bugs to: MMDF@A.CS.OKSTATE.EDU)
P: HELO RELAY.CS.NET
S: 250 a.cs.okstate.edu
P: MAIL FROM:<@RELAY.CS.NET:long@sh.cs.net>
S: 250 OK
P: RCPT TO:<vasoll@a.cs.okstate.edu>
S: 250 Recipient OK.
P: DATA
S: 354 Enter Mail, end by a line with only '.'
P: Date: Tue 9 Jun 87 16:38:19 EDT
P: From: long@sh.cs.net
P: To: vasoll@a.cs.okstate.edu
P:
P: Hello, there.
P: .
S: 250 Submitted & queued (msg.aa00125)
P: TURN
S: 250 OK
P: 220 Server SMTP (Complaints/bugs to MMDF@RELAY.CS.NET)
S: HELO a.cs.okstate.edu
P: 250 RELAY.CS.NET
S: MAIL FROM:<@RELAY.CS.NET:long@sh.cs.net>
P: 250 OK
S: RCPT TO:<vasoll@a.cs.okstate.edu>
P: 250 Recipient OK.
S: DATA
P: 354 Enter Mail, end by a line with only '.'
S: Date: Tue 9 Jun 87 13:33:48 EDT
S: From: vasoll@a.cs.okstate.edu
S: To: long@relay.cs.net
S:
S: It works!
S: .
P: 250 Submitted & queued (msg.aa10744)
S: QUIT
P: 221 session complete at Wed Jun 10 03:58:23.
Often a connection will be made with the remote machine but there will be a problem getting to the point where the smslave begins the link-level protocol. A common error message to see in PHLOG is: ``Timeout while processing script''. This message indicates that a string expected by a ``recv'' command was not matched within the specified number of seconds. Look in the transcript file (specified by the trn= channel parameter which defaults to DEFTRAN, usually ph.trn) to see why the ``recv'' string was not matched.
Often, noise characters can prevent transmitted strings from being received correctly by the remote host. One trick to reduce the possibility of interference is to precede transmitted lines with the remote machine's line-erase character (e.g. xmit ``@username\r'').