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Knowledge base Short Message Service

This page contains technical details and as such may be quite long and hard to follow. If you cannot find the details you require please feel free to contact support who can explain things for you. You will also find many other customers on irc or usenet who can help with queries. Feel free to send us feedback if you think there are any errors in this page.

We offer a number of SMS services.


This is where text messages are sent to us to delivery to our customers. We provide VoIP numbers in all UK area codes and some special services (e.g. 0800). However, at present, only a few of the numbers starting 01 and 02 can receive texts properly from most networks. All of our 01, 02 and 03 numbers can receive texts from Three properly. Attempts to send texts to other geographic numbers (i.e. those starting 01 and 02) cause a call to be made and the text read out by an automated system. We can handle texts to ported in 07 mobile numbers though.

Where texts can be received properly, and this includes all cases where A&A customers send texts through us, the text will be sent on to you by your choice of means. This is based on the incoming text setting on the control pages for your number.


If you simply put in an email address, then the text is emailed to you. Additional email headers may be present to specify fields such as User Data Header if present, etc. This is also the default if you do not put any incoming text handling in to the control pages, but you have an email address defined for the number.


If you include a 19 digit string starting 89 which is the SIM ICCID for one of your SIP2SIM cards then the text will be passed to the SIM directly as a normal text. SIP2SIM charges apply for the SIP2SIM side as an incoming text.


If you put an entry starting http:// or https:// then we will attempt to send the text to you using HTTP (or HTTPS). If the URL ends with a ? or & then an HTTP GET is done with a set of form fields (i.e. name=value) containing information about the text. If the URL does not, then an HTTP POST is done using URL encoded form data.

The fields posted are as follows, but additional fields may be added from time to time.

sctsThe Service Centre Time Stamp in ISO format, which may include time zone. Where the original text has a timestamp, this is used and so may be incorrect or have an unexpected time zone depending on the original SMSC.
oaThe sending number (or name). The format depends on the original text, and this could be a name, or a number, and could be national or international format.
daThe destination number, normally in international number format. This could have an additional digit (sub address) in some cases where our interconnect allows it. The sub address 9 is not normally used.
udhIf there is a User Data Header, then the hex for that header. We concatenate messages where possible (not SIP2SIM MO at present). Note that in this case any concatenation headers are removed and the final concatenated message is passed to you, so this will only be otherUDH fields that may be present.
udThe message encoded in UTF-8 format. The special case is where the message contains a null (e.g. when 8 or 16 bit coding is used and a null included) which is encoded in the invalid UTF-8 sequence 0xC0 0x80.
dcsThe Data Coding Scheme (if not 0), in decimal.
pidThe Protocol Identifier (if not 0), in decimal.

You will note that we have tried to use field names to match GSM 03.40 values. Other values may be included. For legacy reasons you can prefix the URL specified with a * to also send the older field names of timestamp, originator, destination, message.

Outbound messages

We operate an outbound text service that is available to all of our customers that have a VoIP number. To use this service you must have an outgoing password configured in the control pages for the VoIP number.

To send texts you need to issue an HTTP GET or POST to our outbound text gateway https://sms.aa.net.uk/sms.cgi with the following fields as if sent from a form. As the password is sent in plain text you may prefer to use https.

Outbound text messages
usernameThis is the phone number as shown on the control pages for your VoIP number in full international format with no spaces.
passwordThe corresponding outgoing password for the username as set in the control pages for your VoIP number.
daThis is the number to which the message is to be sent and should be a full international format number (however, national format is also accepted). This may be a SIP2SIM ICCID to send direct to a SIM.
udThis is the message to send, encoded in UTF-8.
limitSet this to limit the number of parts that the message may be sent in.
costcentreOptional, up to 10 characters, code that is included in the bill XML data.
privateMarks the message as private, see below
oaSets the sending number (see below). Normally not needed as your username is used.
udhHex UDH header, see below.
srrEmail address or URL for delivery report, see below

Note that we have, again, tried to use GSM 03.40 field names, but alternative field names are supported for now: destination, originator, message.

We support UTF-8 coding of the full GSM 7 bit character set (including £$¥èéùìòÇØøÅåΔ_ΦΓΛΩΠΨΣΘΞÆæÉÄÖÑܧäöñüà€¡¿). Whilst one message is normally up to 160 characters some characters are coded using two characters using an ESC prefix in the 7 bit alphabet (€,[,\,],^,{,|,},~). The message will be coded as 7, 8 or 16 bit depending on what you include in the text, and this will impact the number of message parts that may be sent. If you include the invalid UTF-8 sequence 0xC0 0x80, then that includes a null in the message. If you include any unicode characters beyond U+0xFFFF then UTF-16 coding is used and sending of text in is UCS2 format. Not all interconnects or devices understand UTF-16 format.

The response text starts either ERR: and an error message or OK:

Example, using curl on linux: curl --silent --get --form-string username=01234567890 --form-string password=123456 --form-string da=01234567890 --form-string ud="Hello world" https://sms.aa.net.uk/sms.cgi

Messages are charged at 7.20p per message part.

Send a message now

Delivery reports

In some cases we can provide a delivery report and indicate progress of a message. However this is not always possible and should not be relied on.

To use this, specify the srr either as an email address or a URL. The URL can include (typically after the ?) a string %code which will be replaced with a number that indicates progress. 1=Delivered, 2=Rejected, 4=Buffered, 8=Accepted by SMSC, and 16=Rejected by SMSC. Other % strings can be used such as %da or %dest as the original destination number, %oa for originator, %ud for the message.

Texts to SIP2SIM SIMs

Using our normal text services setting the destination number as the SIM ICCID (19 digit number starting 89) will send the text to the SIM.

You can also use the outgoing text gateway using the SIM ICCID as the username and a password as set in the SIM config on the control pages. In this case you do not need to specify the da.

Multipart texts

Where possible multi-part texts are automatically handled, concatenated before being passed to you, or split from your message in to parts. Unfortunately, not all of the systems to which we interconnect handle multi-part messages sensible, and this can result in a multi-part message being delivered as multiple separate text messages. At present, SIP2SIM MO SMS is delivered as multi-part with UDH for concatenation so if you have your own script it'll need to use the UDH to glue the parts together.

Itemised billing

Your bill will show the number of texts sent and received per number. The optional XML version of your bill contains detailed information for each text sent or received, including the text content of the message (unless the private setting was used).

Multipart texts are itemised and billed as a single text but billed for the number of parts sent. The XML identifies the number of parts.


The originator field is used to set where the message is from. Normally this is only your phone number. Exceptions are:-

  • If you have a presentation number set up for your VoIP, this will be used unless you specify an originator. You can specify the presentation number, or the main number.
  • If you ask us, we can allow sending of text based originators on a per account basis. You will need to be an established customer. This can be withdrawn at any time.