sms

README

sms

A Go library for encoding and decoding SMSs.

sms is a Go library for encoding and decoding SMS TPDUs, as specified in 3GPP TS 23.040 and 3GPP TS 23.038. The initial impetus was to provide functionality to send and receive SMSs via a GSM modem, but the library may be generally useful anywhere encoding and decoding SMS TPDUs or their fields is required.

Features

Supports the following functionality:

• Creation of SMS Submit TPDUs from UTF-8 strings
• Segmentation of large messages into several concatenated SMS Submit TPDUs
• Automatic selection of alphabet and language when encoding
• Decoding of SMS Deliver TPDUs into UTF-8 strings
• Reassembly of concatenated SMS Deliver TPDUs into a single large message
• Supports encoding and decoding all SMS TPDU types, not just Submit and Deliver
• Supports encoding and decoding SMS TPDUs to be sent and recevied via GSM modems in PDU mode

Contained Packages

The tpdu package provides the core TPDU types and conversions to and from their binary form.

Several packages build on top of tpdu to provide higher level functionality:

The sar package provides segmentation and reassembly of concatenated SMS TPDUs to implement large messages.

The message package provides a layer above sar that allows simplfied encoding and decoding of messages with only the message and the destination number.

The pdumode package provides encoding and decoding of PDUs exchanged with GSM modems in PDU mode.

A number of packages provide functionality to encode and decode TPDU fields:

The bcd package provides conversions to and from BCD format.

The gsm7 package provides conversions to and from 7bit packed user data.

The charset package provides the character sets used to encode user data in GSM 7bit format as specified in 3GPP TS 23.038.

The semioctet package provides conversions to and from semioctet format.

The ucs2 package provides conversions between UCS-2 and UTF-8.

Examples

The cmd directory contains basic commands to exercise, debug and demonstrate the core functionality of the library, including:

• decoding arbitrary TPDUs (smsdecode)
• encoding messages into SMS Submit TPDUs (smssubmit)
• decoding SMS Deliver TPDUs into messages (smsdeliver)
• displaying supported character sets (charsets).

The following examples demonstrate the example commands, and their code provides some examples of using the library.

Submit Encoding

Creating an SMS to send:

$ smssubmit -number 12345 -message "Hello world"
Submit TPDU:
010005912143f500000bc8329bfd06dddf723619

Deliver Decoding

Decoding an SMS received from a GSM modem in PDU mode:

$ smsdeliver -p 07911614220991F1040B911605935713F200008140806113912304D7F79B0E
+61503975312: Woot

Concatenated Message Decoding

Concatenating and displaying a message split into multiple Deliver TPDUs.

$ smsdeliver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
+61503975312: this is a very long message that does not fit in a single SMS message, at least it will if I keep adding more to it as 160 characters is more than you might think 😁

General TPDU Decoding

Decoding the Submit TPDU created above:

$ smsdecode -o 010005912143f500000bc8329bfd06dddf723619
(*tpdu.Submit)(0xc4200c0000)({
 TPDU: (tpdu.TPDU) {
  FirstOctet: (uint8) 1,
  PID: (uint8) 0,
  DCS: (uint8) 0,
  UDH: (tpdu.UserDataHeader) <nil>,
  UD: (tpdu.UserData) (len=11 cap=12) {
   00000000  48 65 6c 6c 6f 20 77 6f  72 6c 64                 |Hello world|
  }
 },
 MR: (uint8) 0,
 DA: (tpdu.Address) {
  TOA: (uint8) 145,
  Addr: (string) (len=5) "12345"
 },
 VP: (tpdu.ValidityPeriod) {
  Format: (tpdu.ValidityPeriodFormat) 0,
  Time: (tpdu.Timestamp) 0001-01-01 00:00:00 +0000 UTC,
  Duration: (time.Duration) 0s,
  EFI: (uint8) 0
 }
})