This module implements a generic gsm interface. To function correctly it needs a gsm driver to be loaded, so that the module can use the driver to access the underlying hardware.

The link between the gsm module and the gsm driver is established without the programmer intervetion by the driver itself.

Once the gsm driver is connected to the GSM network, this module can be used to access functionalities at different levels:

  • Network level: query the operators/carriers, select a carrier, retrieve the signal strength, retrieve info about the current cell
  • Device level: retrieve info about IMEI and SIM card
  • Packet Switch Service level: once attached to an APN, the standard socket interface is available. Secure sockets are available if the underlying driver supports them. Due to the nature of GSM networks (private networks behind a NATing APN), listening sockets are not implemented both for UDP and TCP.
  • SMS level: receive, read and send SMS (not yet available)

The following constants are defined:

  • AUTH_NONE, no authentication required with APN
  • AUTH_DETECT, automatic authentication detection
  • AUTH_PAP, use PAP authentication
  • AUTH_CHAP, use CHAP authentication

Translate a host name to IPv4 address format. The IPv4 address is returned as a string, such as “”.

attach(apn, username = "", psw = "", auth = AUTH_NONE, timeout=120000)

Try to establish a link with the chosen Access Point Name apn. auth must be one of AUTH_NONE (default), AUTH_PAP, AUTH_CHAP, AUTH_DETECT. username and psw are optional, depending on the operator. timeout is the time in milliseconds to wait for network registration (connecting to the carrier and receiving GPRS support) and APN negotiation (enabling the packet switch service)

An exception can be raised if the connection is not successful.


Detach from APN.


Return information on the mobile device and SIM card.

The result is a tuple where the elements are, in order:

  • The IMEI as a string
  • The SIM card id as a string

Return information on the currently established APN link.

The result is a tuple where the elements are, in order:

  • The assigned IP as a string
  • The DNS IP as a string

Note that the returned IP, is in the private range and doesn’t match the IP seen by the other end of a socket.


Return information on the GSM network.

The result is a tuple where the elements are, in order:

  • The service type as a string: GMS, UMTS, LTE
  • The MCC as an integer, negative if not known
  • the MNC as an integer, negative if not known
  • The Base Station identifier as string
  • The LAC (location area code) as a string
  • The Cell Identity as a string
  • The registration status to the mobile network: True or False
  • The presence of a link to an APN: True or False

Return an integer representing the signal strength in dB.


Return a 7-integer tuple (YYYY,MM,DD,hh,mm,ss,tz where tz represents the difference in minutes with GMT) representing the current network’s clock time. The underlying gsm driver may require the PIN insertion and/or a network connection before the command execution.


Retrieve the list of available operators/carrier. If the result is None, it was not possible to retrieve the list of operators.

The result is a tuple where each items is a tuple of the following items:

  • type, being 1 if available and 2 if currently connected
  • long name, a string with the full name of the operator
  • short name, a string with the short name of the operator
  • identifier, the numeric identifier of the operator as a string

Try to select the operator with long name opname. It is suggested to retrieve the list of operators before trying to set one.

set_rat(rat, bands=[])

Try to set the Radio Access Technology to use. rat must be one of the constants:

  • samp:GSM: for GSM radio
  • samp:CAT_M1: for LTE Cat M1
  • samp:CAT_NB1: for LTE NB IoT

The argument bands is used to select a subset of bands for the selected RAT. For samp:GSM the available bands are in the set (0,1,2,3) corresponding in order to 900 MHz, 1800MHz, 850MHz and 1900MHz. For LTE bands, the set of available bands can be looked up here (use the Band column).

The underlying gsm driver may not support the RAT or the bands and can raise an exception or ignore unsupported bands.

select(rlist, wlist, xlist, timeout=None)

This is equivalent to the Unix select system call. The first three arguments are sequences of socket instances.

  • rlist: wait until ready for reading
  • wlist: wait until ready for writing
  • xlist: wait for an “exceptional condition” (not supported by every gsm driver)

Empty sequences are allowed. The optional timeout argument specifies a time-out as an integer number in milliseconds. When the timeout argument is omitted the function blocks until at least one socket is ready. A timeout value of zero specifies a poll and never blocks.

The return value is a triple of lists of objects that are ready: subsets of the first three arguments. When the time-out is reached without a socket becoming ready, three empty lists are returned.

list_sms(unread=False, maxsms=10, offset=0)

Return a tuple of received SMS. Each SMS is a tuple with:

  • Text of the message
  • Number of the sender
  • Timestamp of the SMS (7 integer elements YYYY,MM,DD,hh,mm,ss,tz where tz represents the difference in minutes with GMT)
  • SMS index

Parameter unread selects unread SMS only if set to True. maxsms defines the maximum number of SMS to return, while offset selects only SMS with index greater than or equal to offset. If the device stores many SMS, it is suggested to read them in chunks by incrementing offset.

send_sms(num, txt)

Try to send the SMS with text txt to receiver num.

Return an integer representing the index of the SMS (but this may vary from driver to driver!). If the returned integer is negative, it has not been possible to send the SMS. An exception is raised if the underlying drivers fails while sending the SMS.


Delete the SMS identified by index. The value of index to use must be taken from the result of list_sms.


Return the number of SMS received since startup. It is not necessarily equal to the number of unread SMS.


Return a string representing the Short Message Service Center


Set the Short Message Service Center to the value of smsc