471 lines
20 KiB
Plaintext
471 lines
20 KiB
Plaintext
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* Application SMS
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The SMS module for Asterisk was developed by Adrian Kennard, and is an
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implementation of the ETSI specification for landline SMS, ETSI ES 201
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912, which is available from www.etsi.org. Landline SMS is starting to
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be available in various parts of Europe, and is available from BT in
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the UK. However, Asterisk would allow gateways to be created in other
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locations such as the US, and use of SMS capable phones such as the
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Magic Messenger. SMS works using analogue or ISDN lines.
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Background
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Short Message Service (SMS), or texting is very popular between mobile
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phones. A message can be sent between two phones, and normally
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contains 160 characters. There are ways in which various types of data
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can be encoded in a text message such as ring tones, and small
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graphic, etc. Text messaging is being used for voting and
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competitions, and also SPAM...
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Sending a message involves the mobile phone contacting a message
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centre (SMSC) and passing the message to it. The message centre then
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contacts the destination mobile to deliver the message. The SMSC is
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responsible for storing the message and trying to send it until the
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destination mobile is available, or a timeout.
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Landline SMS works in basically the same way. You would normally have
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a suitable text capable landline phone, or a separate texting box such
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as a Magic Messenger on your phone line. This sends a message to a
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message centre your telco provides by making a normal call and sending
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the data using 1200 Baud FSK signaling according to the ETSI spec. To
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receive a message the message centre calls the line with a specific
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calling number, and the text capable phone answers the call and
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receives the data using 1200 Baud FSK signaling. This works
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particularly well in the UK as the calling line identity is sent
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before the first ring, so no phones in the house would ring when a
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message arrives.
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Typical use with Asterisk
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Sending messages from an Asterisk box can be used for a variety of
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reasons, including notification from any monitoring systems, email
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subject lines, etc.
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Receiving messages to an Asterisk box is typically used just to email
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the messages to someone appropriate - we email and texts that are
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received to our direct numbers to the appropriate person. Received
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messages could also be used to control applications, manage
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competitions, votes, post items to IRC, anything.
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Using a terminal such as a magic messenger, an Asterisk box could ask
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as a message centre sending messages to the terminal, which will beep
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and pop up the message (and remember 100 or so messages in its
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memory).
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Terminology
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SMS
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Short Message Service
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i.e. text messages
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SMSC
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Short Message Service Centre
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The system responsible for storing and forwarding messages
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MO
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Mobile Originated
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A message on its way from a mobile or landline device to the SMSC
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MT
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Mobile Terminated
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A message on its way from the SMSC to the mobile or landline device
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RX
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Receive
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A message coming in to the Asterisk box
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TX
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Transmit
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A message going out of the Asterisk box
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Sub address
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When sending a message to a landline, you simply send to the landline
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number. In the UK, all of the mobile operators (bar one) understand
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sending messages to landlines and pass the messages to the BTText
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system for delivery to the landline.
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The specification for landline SMS allows for the possibility of more
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than one device on a single landline. These can be configured with Sub
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addresses which are a single digit. To send a message to a specific
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device the message is sent to the landline number with an extra digit
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appended to the end. The telco can define a default sub address (9 in
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the UK) which is used when the extra digit is not appended to the end.
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When the call comes in, part of the calling line ID is the sub
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address, so that only one device on the line answers the call and
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receives the message.
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Sub addresses also work for outgoing messages. Part of the number
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called by the device to send a message is its sub address. Sending
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from the default sub address (9 in the UK) means the message is
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delivered with the sender being the normal landline number. Sending
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from any other sub address makes the sender the landline number with
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an extra digit on the end.
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Using Asterisk, you can make use of the sub addresses for sending and
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receiving messages. Using DDI (DID, i.e. multiple numbers on the line
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on ISDN) you can also make use of many different numbers for SMS.
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Build / installation
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app_sms.c is included in the Asterisk source apps directory and is
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included in the object list (app_sms.so) in apps/Makefile.
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smsq.c is a stand alone helper application which is used to send SMSs
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from the command line. It uses the popt library. A line for your make
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file is:-
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smsq: smsq.c
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cc -O -o smsq smsq.c -lpopt
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extensions.conf
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The following contexts are recommended.
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; Mobile Terminated, RX. This is used when an incoming call from the SMS arrive
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s, with the queue (called number and sub address) in ${EXTEN}
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; Running an app after receipt of the text allows the app to find all messages
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in the queue and handle them, e.g. email them.
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; The app may be something like smsq --process=somecommand --queue=${EXTEN}
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to run a command for each received message
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; See below for usage
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[smsmtrx]
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exten = _X.,1, SMS(${EXTEN}|a)
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exten = _X.,2,System("someapptohandleincomingsms ${EXTEN}")
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exten = _X.,3,Hangup
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; Mobile originated, RX. This is receiving a message from a device, e.g. a Magi
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c Messenger on a sip extension
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; Running an app after receipt of the text allows the app to find all messages
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in the queue and handle then, e.g. sending them to the public SMSC
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; The app may be something like smsq --process=somecommand --queue=${EXTEN}
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to run a command for each received message
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; See below for example usage
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[smsmorx]
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exten = _X.,1, SMS(${EXTEN}|sa)
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exten = _X.,2,System("someapptohandlelocalsms ${EXTEN}")
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exten = _X.,3,Hangup
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smsmtrx is normally accessed by an incoming call from the SMSC. In the
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UK this call is from a CLI of 080058752X0 where X is the sub address.
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As such a typical usage in the extensions.conf at the point of
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handling an incoming call is:-
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exten = _X./8005875290,1,Goto(smsmtrx,${EXTEN},1)
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exten = _X./_80058752[0-8]0,1,Goto(smsmtrx,${EXTEN}-${CALLERIDNUM:8:1},1)
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Alternatively, if you have the correct national prefix on incoming
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CLI, e.g. using zaphfc, you might use:-
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exten = _X./08005875290,1,Goto(smsmtrx,${EXTEN},1)
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exten = _X./_080058752[0-8]0,1,Goto(smsmtrx,${EXTEN}-${CALLERIDNUM:9:1},1)
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smsmorx is normally accessed by a call from a local sip device
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connected to a Magic Messenger. It could however by that you are
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operating Asterisk as a message centre for calls from outside. Either
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way, you look at the called number and goto smsmorx. In the UK, the
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SMSC number that would be dialed is 1709400X where X is the caller sub
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address. As such typical usage in extension.config at the point of
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handling a call from a sip phone is:-
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exten = 17094009,1,Goto(smsmorx,${CALLERIDNUM},1)
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exten = _1709400[0-8],1,Goto(smsmorx,${CALLERIDNUM}-{EXTEN:7:1},1)
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Using smsq
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smsq is a simple helper application designed to make it easy to send
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messages from a command line. it is intended to run on the Asterisk
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box and have direct access to the queue directories for SMS and for
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Asterisk.
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In its simplest form you can send an SMS by a command such as
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smsq 0123456789 This is a test to 0123456789
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This would create a queue file for a mobile originated TX message in
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queue 0 to send the text "This is a test to 0123456789" to 0123456789.
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It would then place a file in the /var/spool/asterisk/outgoing
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directory to initiate a call to 17094009 (the default message centre
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in smsq) attached to application SMS with argument of the queue name
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(0).
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Normally smsq will queue a message ready to send, and will then create
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a file in the Asterisk outgoing directory causing Asterisk to actually
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connect to the message centre or device and actually send the pending
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message(s).
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Using --process, smsq can however be used on received queues to run a
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command for each file (matching the queue if specified) with various
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environment variables set based on the message (see below);
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smsq options:-
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--help
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Show help text
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--usage
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Show usage
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--queue
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-q
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Specify a specific queue
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In no specified, messages are queued under queue "0"
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--da
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-d
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Specify destination address
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--oa
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-o
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Specify originating address
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This also implies that we are generating a mobile terminated message
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--ud
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-m
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Specify the actual message
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--ud-file
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-f
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Specify a file to be read for the context of the message
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A blank filename (e.g. --ud-file= on its own) means read stdin. Very
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useful when using via ssh where command line parsing could mess up the
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message.
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--mt
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-t
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Mobile terminated message to be generated
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--mo
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Mobile originated message to be generated
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Default
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--tx
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Transmit message
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Default
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--rx
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-r
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Generate a message in the receive queue
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--UTF-8
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Treat the file as UTF-8 encoded (default)
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--UCS-1
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Treat the file as raw 8 bit UCS-1 data, not UTF-8 encoded
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--UCS-2
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Treat the file as raw 16 bit bigendian USC-2 data
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--process
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Specific a command to process for each file in the queue
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Implies --rx and --mt if not otherwise specified.
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Sets environment variables for every possible variable, and also ud,
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ud8 (USC-1 hex), and ud16 (USC-2 hex) for each call. Removes files.
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--motx-channel
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Specify the channel for motx calls
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May contain X to use sub address based on queue name or may be full
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number
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Default is Local/1709400X
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--motx-callerid
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Specify the caller ID for motx calls
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The default is the queue name without -X suffix
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--motx-wait
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Wait time for motx call
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Default 10
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--motx-delay
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Retry time for motx call
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Default 1
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--motx-retries
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Retries for motx call
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Default 10
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--mttx-channel
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Specify the channel for mttx calls
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Default is Local/ and the queue name without -X suffix
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--mtttx-callerid
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Specify the callerid for mttx calls
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May include X to use sub address based on queue name or may be full
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number
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Default is 080058752X0
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--mttx-wait
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Wait time for mttx call
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Default 10
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--mttx-delay
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Retry time for mttx call
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Default 30
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--mttx-retries
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Retries for mttx call
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Default 100
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--default-sub-address
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The default sub address assumed (e.g. for X in CLI and dialled numbers
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as above) when none added (-X) to queue
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Default 9
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--no-dial
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-x
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Create queue, but do not dial to send message
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--no-wait
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Do not wait if a call appears to be in progress
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This could have a small window where a mesdsage is queued but not
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sent, so regular calls to smsq should be done to pick up any missed
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messages
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--concurrent
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How many concurrent calls to allow (per queue), default 1
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--mr
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-n
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Message reference
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--pid
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-p
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Protocol ID
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--dcs
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Data coding scheme
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--udh
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Specific hex string of user data header specified (not including the
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initial length byte)
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May be a blank string to indicate header is included in the user data
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already but user data header indication to be set.
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--srr
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Status report requested
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--rp
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Return path requested
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--vp
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Specify validity period (seconds)
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--scts
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Specify timestamp (YYYY-MM-DDTHH:MM:SS)
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--spool-dir
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Spool dir (in which sms and outgoing are found)
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Default /var/spool/asterisk
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Other arguments starting '-' or '--' are invalid and will cause an
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error. Any trailing arguments are processed as follows:-
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* If the message is mobile originating and no destination address
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has been specified, then the first argument is assumed to be a
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destination address
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* If the message is mobile terminating and no destination address
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has been specified, then the first argument is assumed to be the
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queue name
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* If there is no user data, or user data file specified, then any
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following arguments are assumed to be the message, which are
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concatenated.
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* If no user data is specified, then no message is sent. However,
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unless --no-dial is specified, smsq checks for pending messages
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and generates an outgoing anyway
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Note that when smsq attempts to make a file in
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/var/spool/asterisk/outgoing, it checks if there is already a call
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queued for that queue. It will try several filenames, up to the
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--concorrent setting. If these files exists, then this means Asterisk
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is already queued to send all messages for that queue, and so Asterisk
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should pick up the message just queued. However, this alone could
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create a race condition, so if the files exist then smsq will wait up
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to 3 seconds to confirm it still exists or if the queued messages have
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been sent already. The --no-wait turns off this behaviour. Basically,
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this means that if you have a lot of messages to send all at once,
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Asterisk will not make unlimited concurrent calls to the same message
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centre or device for the same queue. This is because it is generally
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more efficient to make one call and send all of the messages one after
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the other.
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smsq can be used with no arguments, or with a queue name only, and it
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will check for any pending messages and cause an outgoing if there are
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any. It only sets up one outgoing call at a time based on the first
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queued message it finds. A outgoing call will normally send all queued
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messages for that queue. One way to use smsq would be to run with no
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queue name (so any queue) every minute or every few seconds to send
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pending message. This is not normally necessary unless --no-dial is
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selected. Note that smsq does only check motx or mttx depending on the
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options selected, so it would need to be called twice as a general
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check.
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UTF-8 is used to parse command line arguments for user data, and is
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the default when reading a file. If an invalid UTF-8 sequence is
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found, it is treated as UCS-1 data (i.e, as is).
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The --process option causes smsq to scan the specified queue (default
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is mtrx) for messages (matching the queue specified, or any if queue
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not specified) and run a command and delete the file. The command is
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run with a number of environment variables set as follows. Note that
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these are unset if not needed and not just taken from the calling
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environment. This allows simple processing of incoming messages
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$queue
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Set if a queue specified
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$?srr
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srr is set (to blank) if srr defined and has value 1.
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$?rp
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rp is set (to blank) if rp defined and has value 1.
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$ud
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User data, UTF-8 encoding, including any control characters, but with
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nulls stripped out
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Useful for the content of emails, for example, as it includes any
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newlines, etc.
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$ude
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User data, escaped UTF-8, including all characters, but control
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characters \n, \r, \t, \f, \xxx and \ is escaped as \\
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Useful fGuaranteed one line printable text, so useful in Subject lines
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of emails, etc
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$ud8
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Hex UCS-1 coding of user data (2 hex digits per character)
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Present only if all user data is in range U+0000 to U+00FF
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$ud16
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Hex UCS-2 coding of user data (4 hex digits per chartacter)
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other
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Other fields set using their field name, e.g. mr, pid, dcs, etc. udh
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is a hex byte string
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File formats
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By default all queues are held in a director /var/spool/asterisk/sms.
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Within this directory are sub directories mtrx, mttx, morx, motx which
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hold the received messages and the messages ready to send. Also,
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/var/log/asterisk/sms is a log file of all messages handled.
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The file name in each queue directory starts with the queue parameter
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to SMS which is normally the CLI used for an outgoing message or the
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called number on an incoming message, and may have -X (X being sub
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address) appended. If no queue ID is known, then 0 is used by smsq by
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default. After this is a dot, and then any text. Files are scanned for
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matching queue ID and a dot at the start. This means temporary files
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being created can be given a different name not starting with a queue
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(we recommend a . on the start of the file name for temp files).
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Files in these queues are in the form of a simple text file where each
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line starts with a keyword and an = and then data. udh and ud have
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options for hex encoding, see below.
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UTF-8. The user data (ud) field is treated as being UTF-8 encoded
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unless the DCS is specified indicating 8 bit formart. If 8 bit format
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is specified then the user data is sent as is.
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The keywords are as follows:-
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oa Originating address
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The phone number from which the message came
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Present on mobile terminated messages and is the CLI for morx messages
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da
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Destination Address
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The phone number to which the message is sent
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Present on mobile originated messages
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scts
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The service centre time stamp
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Format YYYY-MM-DDTHH:MM:SS
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Present on mobile terminated messages
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pid
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One byte decimal protocol ID
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See GSM specs for more details
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Normally 0 or absent
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dcs
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One byte decimal data coding scheme
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If omitted, a sensible default is used (see below)
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See GSM specs for more details
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mr
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One byte decimal message reference
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Present on mobile originated messages, added by default if absent
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srr
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0 or 1 for status report request
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Does not work in UK yet, not implemented in app_sms yet
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rp
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0 or 1 return path
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See GSM specs for details
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vp
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Validity period in seconds
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Does not work in UK yet
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udh
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Hex string of user data header prepended to the SMS contents,
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excluding initial length byte.
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Consistent with ud, this is specified as udh# rather than udh=
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If blank, this means that the udhi flag will be set but any user data
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header must be in the ud field
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ud
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User data, may be text, or hex, see below
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udh is specified as as udh# followed by hex (2 hex digits per byte).
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If present, then the user data header indicator bit is set, and the
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length plus the user data header is added to the start of the user
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data, with padding if necessary (to septet boundary in 7 bit format).
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User data can hold an USC character codes U+0000 to U+FFFF. Any other
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characters are coded as U+FEFF
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ud can be specified as ud= followed by UTF-8 encoded text if it
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contains no control characters, i.e. only (U+0020 to U+FFFF). Any
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invalid UTF-8 sequences are treated as is (U+0080-U+00FF).
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ud can also be specified as ud# followed by hex (2 hex digits per
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byte) containing characters U+0000 to U+00FF only.
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ud can also be specified as ud## followed by hex (4 hex digits per
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byte) containing UCS-2 characters.
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When written by app_sms (e.g. incoming messages), the file is written
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with ud= if it can be (no control characters). If it cannot, the a
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comment line ;ud= is used to show the user data for human readability
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and ud# or ud## is used.
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Delivery reports
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The SMS specification allows for delivery reports. These are requested
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using the srr bit. However, as these do not work in the UK yet they
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are not fully implemented in this application. If anyone has a telco
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that does implement these, please let me know. BT in the UK have a non
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standard way to do this by starting the message with *0#, and so this
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application may have a UK specific bodge in the near future to handle
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these.
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The main changes that are proposed for delivery report handling are :-
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* New queues for sent messages, one file for each destination
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address and message reference.
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* New field in message format, user reference, allowing applications
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to tie up their original message with a report.
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* Handling of the delivery confirmation/rejection and connecting to
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the outgoing message - the received message file would then have
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fields for the original outgoing message and user reference
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allowing applications to handle confirmations better.
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