How can I retrieve the signal strength of nearby w

Question

How can I retrieve the signal strength of nearby wireless LAN networks on Windows using Python?

I would like to either show or graph the values.

Answer 1

@fmark I just wanted to say THANK YOU so much for this awesome post. At my work I have been trying to get RSSI from the connected AP in Windows, and you deserve many thanks for me finally getting it done. I'm currently listing all APs, but I'm working on modifying it. I wanted to offer a recommendation towards your code. I'm not very experienced with C or the Python CTypes module, but I think I might have found a possible bug. I'm really not sure what difference it makes, but I noticed:

You define enums like this:

DOT11_BSS_TYPE = c_uint
(dot11_BSS_type_infrastructure,
 dot11_BSS_type_independent,
 dot11_BSS_type_any) = map(DOT11_BSS_TYPE, xrange(1, 4))

But then other times you define something very similar like this:

DOT11_PHY_TYPE = c_uint
dot11_phy_type_unknown      = 0
dot11_phy_type_any          = 0
dot11_phy_type_fhss         = 1
dot11_phy_type_dsss         = 2
dot11_phy_type_irbaseband   = 3
dot11_phy_type_ofdm         = 4
dot11_phy_type_hrdsss       = 5
dot11_phy_type_erp          = 6
dot11_phy_type_ht           = 7
dot11_phy_type_IHV_start    = 0x80000000
dot11_phy_type_IHV_end      = 0xffffffff 

I think the second snippit should be modeled like the first, but I could be wrong. Here was my idea:

DOT11_PHY_TYPE = c_uint
(dot11_phy_type_unknown,
 dot11_phy_type_any,
 dot11_phy_type_fhss,
 dot11_phy_type_dsss,
 dot11_phy_type_irbaseband,
 dot11_phy_type_ofdm,
 dot11_phy_type_hrdsss,
 dot11_phy_type_erp,
 dot11_phy_type_ht,
 dot11_phy_type_IHV_start,
 dot11_phy_type_IHV_end) = map(DOT11_PHY_TYPE,
                               [0,0,1,2,3,4,
                                5,6,7,0x80000000,
                                0xffffffff])

This way those values would get correctly mapped to DOT11_PHY_TYPE. Perhaps I am completely wrong, but for future folks like myself, I just wanted whatever is stumbled on here to be correct :) Thanks again, @fmark.

Answer 2

If you don't want to deal with Windows API you could use method shown here with a slight modification.

You can use this command:

netsh wlan show networks mode=Bssid

using this code

import subprocess
results = subprocess.check_output(["netsh", "wlan", "show", "network", "mode=Bssid"])

This will give you additiona "Signal" information as a percentage. This can be converted to RSSI using this method.

Answer 3

Well you could invoke the system command to get that info (Linux = iwlist), parse the result, and display it.

Answer 4

So.. I based myself on @fmarks code (which was a live-safer for me), and you should add the WlanScan function, or else the RSSI values will not refresh.

Here is my extended code!

All props to @fmarks!

__author__ = 'Pedro Gomes'

import time
from ctypes import *
from ctypes.wintypes import *
from sys import exit

def customresize(array, new_size):
    return (array._type_*new_size).from_address(addressof(array))

wlanapi = windll.LoadLibrary('wlanapi.dll')

ERROR_SUCCESS = 0

class GUID(Structure):
    _fields_ = [
        ('Data1', c_ulong),
        ('Data2', c_ushort),
        ('Data3', c_ushort),
        ('Data4', c_ubyte*8),
        ]

WLAN_INTERFACE_STATE = c_uint
(wlan_interface_state_not_ready,
 wlan_interface_state_connected,
 wlan_interface_state_ad_hoc_network_formed,
 wlan_interface_state_disconnecting,
 wlan_interface_state_disconnected,
 wlan_interface_state_associating,
 wlan_interface_state_discovering,
 wlan_interface_state_authenticating) = map(WLAN_INTERFACE_STATE, xrange(0, 8))

class WLAN_INTERFACE_INFO(Structure):
    _fields_ = [
        ("InterfaceGuid", GUID),
        ("strInterfaceDescription", c_wchar * 256),
        ("isState", WLAN_INTERFACE_STATE)
    ]

class WLAN_INTERFACE_INFO_LIST(Structure):
    _fields_ = [
        ("NumberOfItems", DWORD),
        ("Index", DWORD),
        ("InterfaceInfo", WLAN_INTERFACE_INFO * 1)
    ]

WLAN_MAX_PHY_TYPE_NUMBER = 0x8
DOT11_SSID_MAX_LENGTH = 32
WLAN_REASON_CODE = DWORD

DOT11_BSS_TYPE = c_uint
(dot11_BSS_type_infrastructure,
 dot11_BSS_type_independent,
 dot11_BSS_type_any) = map(DOT11_BSS_TYPE, xrange(1, 4))

DOT11_PHY_TYPE = c_uint
dot11_phy_type_unknown      = 0
dot11_phy_type_any          = 0
dot11_phy_type_fhss         = 1
dot11_phy_type_dsss         = 2
dot11_phy_type_irbaseband   = 3
dot11_phy_type_ofdm         = 4
dot11_phy_type_hrdsss       = 5
dot11_phy_type_erp          = 6
dot11_phy_type_ht           = 7
dot11_phy_type_IHV_start    = 0x80000000
dot11_phy_type_IHV_end      = 0xffffffff

DOT11_AUTH_ALGORITHM = c_uint
DOT11_AUTH_ALGO_80211_OPEN         = 1
DOT11_AUTH_ALGO_80211_SHARED_KEY   = 2
DOT11_AUTH_ALGO_WPA                = 3
DOT11_AUTH_ALGO_WPA_PSK            = 4
DOT11_AUTH_ALGO_WPA_NONE           = 5
DOT11_AUTH_ALGO_RSNA               = 6
DOT11_AUTH_ALGO_RSNA_PSK           = 7
DOT11_AUTH_ALGO_IHV_START          = 0x80000000
DOT11_AUTH_ALGO_IHV_END            = 0xffffffff

DOT11_CIPHER_ALGORITHM = c_uint
DOT11_CIPHER_ALGO_NONE            = 0x00
DOT11_CIPHER_ALGO_WEP40           = 0x01
DOT11_CIPHER_ALGO_TKIP            = 0x02
DOT11_CIPHER_ALGO_CCMP            = 0x04
DOT11_CIPHER_ALGO_WEP104          = 0x05
DOT11_CIPHER_ALGO_WPA_USE_GROUP   = 0x100
DOT11_CIPHER_ALGO_RSN_USE_GROUP   = 0x100
DOT11_CIPHER_ALGO_WEP             = 0x101
DOT11_CIPHER_ALGO_IHV_START       = 0x80000000
DOT11_CIPHER_ALGO_IHV_END         = 0xffffffff

WLAN_AVAILABLE_NETWORK_CONNECTED = 1
WLAN_AVAILABLE_NETWORK_HAS_PROFILE = 2

WLAN_AVAILABLE_NETWORK_INCLUDE_ALL_ADHOC_PROFILES = 0x00000001
WLAN_AVAILABLE_NETWORK_INCLUDE_ALL_MANUAL_HIDDEN_PROFILES = 0x00000002

class DOT11_SSID(Structure):
    _fields_ = [
        ("SSIDLength", c_ulong),
        ("SSID", c_char * DOT11_SSID_MAX_LENGTH)
    ]


class WLAN_AVAILABLE_NETWORK(Structure):
    _fields_ = [
        ("ProfileName", c_wchar * 256),
        ("dot11Ssid", DOT11_SSID),
        ("dot11BssType", DOT11_BSS_TYPE),
        ("NumberOfBssids", c_ulong),
        ("NetworkConnectable", c_bool),
        ("wlanNotConnectableReason", WLAN_REASON_CODE),
        ("NumberOfPhyTypes", c_ulong),
        ("dot11PhyTypes", DOT11_PHY_TYPE * WLAN_MAX_PHY_TYPE_NUMBER),
        ("MorePhyTypes", c_bool),
        ("wlanSignalQuality", c_ulong),
        ("SecurityEnabled", c_bool),
        ("dot11DefaultAuthAlgorithm", DOT11_AUTH_ALGORITHM),
        ("dot11DefaultCipherAlgorithm", DOT11_CIPHER_ALGORITHM),
        ("Flags", DWORD),
        ("Reserved", DWORD)
    ]

class WLAN_AVAILABLE_NETWORK_LIST(Structure):
    _fields_ = [
        ("NumberOfItems", DWORD),
        ("Index", DWORD),
        ("Network", WLAN_AVAILABLE_NETWORK * 1)
    ]


DOT11_MAC_ADDRESS = c_ubyte * 6

DOT11_CIPHER_ALGORITHM = c_uint
DOT11_CIPHER_ALGO_NONE            = 0x00
DOT11_CIPHER_ALGO_WEP40           = 0x01
DOT11_CIPHER_ALGO_TKIP            = 0x02

DOT11_PHY_TYPE = c_uint
DOT11_PHY_TYPE_UNKNOWN  = 0
DOT11_PHY_TYPE_ANY         = 0
DOT11_PHY_TYPE_FHSS        = 1
DOT11_PHY_TYPE_DSSS        = 2
DOT11_PHY_TYPE_IRBASEBAND  = 3
DOT11_PHY_TYPE_OFDM        = 4
DOT11_PHY_TYPE_HRDSSS      = 5
DOT11_PHY_TYPE_ERP         = 6
DOT11_PHY_TYPE_HT          = 7
DOT11_PHY_TYPE_IHV_START   = 0X80000000
DOT11_PHY_TYPE_IHV_END     = 0XFFFFFFFF

class WLAN_RATE_SET(Structure):
    _fields_ = [
        ("uRateSetLength", c_ulong),
        ("usRateSet", c_ushort * 126)
    ]

class WLAN_BSS_ENTRY(Structure):
    _fields_ = [
        ("dot11Ssid",DOT11_SSID),
        ("uPhyId",c_ulong),
        ("dot11Bssid", DOT11_MAC_ADDRESS),
        ("dot11BssType", DOT11_BSS_TYPE),
        ("dot11BssPhyType", DOT11_PHY_TYPE),
        ("lRssi", c_long),
        ("uLinkQuality", c_ulong),
        ("bInRegDomain", c_bool),
        ("usBeaconPeriod",c_ushort),
        ("ullTimestamp", c_ulonglong),
        ("ullHostTimestamp",c_ulonglong),
        ("usCapabilityInformation",c_ushort),
        ("ulChCenterFrequency", c_ulong),
        ("wlanRateSet",WLAN_RATE_SET),
        ("ulIeOffset", c_ulong),
        ("ulIeSize", c_ulong)]

class WLAN_BSS_LIST(Structure):
    _fields_ = [
        ("TotalSize", DWORD),
        ("NumberOfItems", DWORD),
        ("NetworkBSS", WLAN_BSS_ENTRY * 1)
    ]

class WLAN_AVAILABLE_NETWORK_LIST_BSS(Structure):
    _fields_ = [
        ("TotalSize", DWORD),
        ("NumberOfItems", DWORD),
        ("Network", WLAN_BSS_ENTRY * 1)
    ]

WlanOpenHandle = wlanapi.WlanOpenHandle
WlanOpenHandle.argtypes = (DWORD, c_void_p, POINTER(DWORD), POINTER(HANDLE))
WlanOpenHandle.restype = DWORD

WlanCloseHandle = wlanapi.WlanCloseHandle
WlanCloseHandle.argtypes = (HANDLE, c_void_p)
WlanCloseHandle.restype = DWORD

WlanEnumInterfaces = wlanapi.WlanEnumInterfaces
WlanEnumInterfaces.argtypes = (HANDLE, c_void_p,
                               POINTER(POINTER(WLAN_INTERFACE_INFO_LIST)))
WlanEnumInterfaces.restype = DWORD

WlanGetAvailableNetworkList = wlanapi.WlanGetAvailableNetworkList
WlanGetAvailableNetworkList.argtypes = (HANDLE, POINTER(GUID), DWORD, c_void_p,
                                        POINTER(POINTER(WLAN_AVAILABLE_NETWORK_LIST)))
WlanGetAvailableNetworkList.restype = DWORD

WlanGetNetworkBssList = wlanapi.WlanGetNetworkBssList
WlanGetNetworkBssList.argtypes = (HANDLE, POINTER(GUID),POINTER(GUID),POINTER(GUID), c_bool, c_void_p,
                                  POINTER(POINTER(WLAN_BSS_LIST)))
WlanGetNetworkBssList.restype = DWORD


WlanFreeMemory = wlanapi.WlanFreeMemory
WlanFreeMemory.argtypes = [c_void_p]


WlanScan = wlanapi.WlanScan
WlanScan.argtypes = (HANDLE, POINTER(GUID),c_void_p,c_void_p, c_void_p)
WlanScan.restype = DWORD




def get_interface():

    NegotiatedVersion = DWORD()
    ClientHandle = HANDLE()
    ret = WlanOpenHandle(1, None, byref(NegotiatedVersion), byref(ClientHandle))
    if ret != ERROR_SUCCESS:
        exit(FormatError(ret))
        # find all wireless network interfaces
    pInterfaceList = pointer(WLAN_INTERFACE_INFO_LIST())
    ret = WlanEnumInterfaces(ClientHandle, None, byref(pInterfaceList))
    if ret != ERROR_SUCCESS:
        exit(FormatError(ret))
    try:
        ifaces = customresize(pInterfaceList.contents.InterfaceInfo,
                              pInterfaceList.contents.NumberOfItems)
        # find each available network for each interface
        for iface in ifaces:
            #print "Interface: %s" % (iface.strInterfaceDescription)
            interface = iface.strInterfaceDescription

    finally:
        WlanFreeMemory(pInterfaceList)
        return interface

class MAC_BSSID_POWER:
    """Classe para os valores retirados"""
    def __init__(self, mac, bssid):

        self.mac = str(mac)
        self.bssid = str(bssid)
        self.valores = []

    def addPower(self,power):
        self.valores.append(int(power))

    def getBssid(self):
        return self.bssid
    def getPowers(self):
        return self.valores
    def getMac(self):
        return self.mac


def get_BSSI():

    BSSI_Values={}

    NegotiatedVersion = DWORD()
    ClientHandle = HANDLE()
    ret = WlanOpenHandle(1, None, byref(NegotiatedVersion), byref(ClientHandle))
    if ret != ERROR_SUCCESS:
        exit(FormatError(ret))
        # find all wireless network interfaces
    pInterfaceList = pointer(WLAN_INTERFACE_INFO_LIST())
    ret = WlanEnumInterfaces(ClientHandle, None, byref(pInterfaceList))
    if ret != ERROR_SUCCESS:
        exit(FormatError(ret))
    try:
        ifaces = customresize(pInterfaceList.contents.InterfaceInfo,
                              pInterfaceList.contents.NumberOfItems)
        # find each available network for each interface
        for iface in ifaces:
            # print "Interface: %s" % (iface.strInterfaceDescription)

            pAvailableNetworkList2 = pointer(WLAN_BSS_LIST())


            ret2 = WlanGetNetworkBssList(ClientHandle,
                                         byref(iface.InterfaceGuid),
                                         None,
                                         None,True,None,
                                         byref(pAvailableNetworkList2))
            if ret2 != ERROR_SUCCESS:
                exit(FormatError(ret2))
            try:
                retScan = WlanScan(ClientHandle,byref(iface.InterfaceGuid),None,None,None)
                if retScan != ERROR_SUCCESS:
                    exit(FormatError(retScan))
                avail_net_list2 = pAvailableNetworkList2.contents
                networks2 = customresize(avail_net_list2.NetworkBSS,
                                         avail_net_list2.NumberOfItems)

                for network in networks2:

                    SSID = str(network.dot11Ssid.SSID[:network.dot11Ssid.SSIDLength])
                    BSSID = ':'.join('%02x' % b for b in network.dot11Bssid).upper()
                    signal_strength = str(network.lRssi)

                #    print "SSID: " + SSID + " BSSID: "+ BSSID+ " SS: "+signal_strength

                    BSSI_Values[BSSID] = [SSID,signal_strength]

                    #print "Total "+str(len(networks2))
                    #print BSSI_Values

            finally:
                WlanFreeMemory(pAvailableNetworkList2)
                WlanCloseHandle(ClientHandle,None)
    finally:
        WlanFreeMemory(pInterfaceList)
    return BSSI_Values


def get_BSSI_times_and_total_seconds(times,seconds):

    BSSI_to_return = {}

    for i in range(0,seconds*times):
        time_to_sleep = float(1.0/times)
        time.sleep(time_to_sleep)
        got_bssi_temp = get_BSSI()

        for bssi in got_bssi_temp:
            if not BSSI_to_return.get(bssi):
                BSSI_to_return[bssi] = MAC_BSSID_POWER(bssi,got_bssi_temp[bssi][0])
                BSSI_to_return[bssi].addPower( got_bssi_temp[bssi][1] )

                #BSSI_to_return[bssi] = [got_bssi_temp[bssi][1]]

            else:
                BSSI_to_return[bssi].addPower( got_bssi_temp[bssi][1] )
                #BSSI_to_return[bssi].append(got_bssi_temp[bssi][1])
        print "Medicao "+str(i)+" de "+str(seconds*times)
    print BSSI_to_return
    return BSSI_to_return



if __name__ == '__main__':

    #print get_interface()
    import time
    test = get_BSSI()
    for i in range(0,10):
        time.sleep(0.5)
        oldTest = test
        test = get_BSSI()
        print "Teste: "+str(i)
        if oldTest == test:
            print "IGUAL"
        else:
            print "DIFERENTE"
        print test
    print "End"

Answer 5

If you are on Windows, you probably want to use the WLAN API, which provides the 'WlanGetAvailableNetworkList()' function (see the API docs for usage). I am not aware of any python wrappers for WLANAPI.DLL so you may have to wrap it yourself using ctypes. I have a preliminary script that does this (works-for-me), but it may be crufty. You'll want to read the documentation to understand the meaning of all the fields:

from ctypes import *
from ctypes.wintypes import *
from sys import exit


def customresize(array, new_size):
    return (array._type_*new_size).from_address(addressof(array))

wlanapi = windll.LoadLibrary('wlanapi.dll')

ERROR_SUCCESS = 0

class GUID(Structure):
    _fields_ = [
        ('Data1', c_ulong),
        ('Data2', c_ushort),
        ('Data3', c_ushort),
        ('Data4', c_ubyte*8),
        ]

WLAN_INTERFACE_STATE = c_uint
(wlan_interface_state_not_ready,
 wlan_interface_state_connected,
 wlan_interface_state_ad_hoc_network_formed,
 wlan_interface_state_disconnecting,
 wlan_interface_state_disconnected,
 wlan_interface_state_associating,
 wlan_interface_state_discovering,
 wlan_interface_state_authenticating) = map(WLAN_INTERFACE_STATE, range(0, 8))

class WLAN_INTERFACE_INFO(Structure):
    _fields_ = [
        ("InterfaceGuid", GUID),
        ("strInterfaceDescription", c_wchar * 256),
        ("isState", WLAN_INTERFACE_STATE)
        ]

class WLAN_INTERFACE_INFO_LIST(Structure):
    _fields_ = [
        ("NumberOfItems", DWORD),
        ("Index", DWORD),
        ("InterfaceInfo", WLAN_INTERFACE_INFO * 1)
        ]

WLAN_MAX_PHY_TYPE_NUMBER = 0x8
DOT11_SSID_MAX_LENGTH = 32
WLAN_REASON_CODE = DWORD
DOT11_BSS_TYPE = c_uint
(dot11_BSS_type_infrastructure,
 dot11_BSS_type_independent,
 dot11_BSS_type_any) = map(DOT11_BSS_TYPE, range(1, 4))
DOT11_PHY_TYPE = c_uint
dot11_phy_type_unknown      = 0
dot11_phy_type_any          = 0
dot11_phy_type_fhss         = 1
dot11_phy_type_dsss         = 2
dot11_phy_type_irbaseband   = 3
dot11_phy_type_ofdm         = 4
dot11_phy_type_hrdsss       = 5
dot11_phy_type_erp          = 6
dot11_phy_type_ht           = 7
dot11_phy_type_IHV_start    = 0x80000000
dot11_phy_type_IHV_end      = 0xffffffff 

DOT11_AUTH_ALGORITHM = c_uint
DOT11_AUTH_ALGO_80211_OPEN         = 1
DOT11_AUTH_ALGO_80211_SHARED_KEY   = 2
DOT11_AUTH_ALGO_WPA                = 3
DOT11_AUTH_ALGO_WPA_PSK            = 4
DOT11_AUTH_ALGO_WPA_NONE           = 5
DOT11_AUTH_ALGO_RSNA               = 6
DOT11_AUTH_ALGO_RSNA_PSK           = 7
DOT11_AUTH_ALGO_IHV_START          = 0x80000000
DOT11_AUTH_ALGO_IHV_END            = 0xffffffff

DOT11_CIPHER_ALGORITHM = c_uint
DOT11_CIPHER_ALGO_NONE            = 0x00
DOT11_CIPHER_ALGO_WEP40           = 0x01
DOT11_CIPHER_ALGO_TKIP            = 0x02
DOT11_CIPHER_ALGO_CCMP            = 0x04
DOT11_CIPHER_ALGO_WEP104          = 0x05
DOT11_CIPHER_ALGO_WPA_USE_GROUP   = 0x100
DOT11_CIPHER_ALGO_RSN_USE_GROUP   = 0x100
DOT11_CIPHER_ALGO_WEP             = 0x101
DOT11_CIPHER_ALGO_IHV_START       = 0x80000000
DOT11_CIPHER_ALGO_IHV_END         = 0xffffffff 

WLAN_AVAILABLE_NETWORK_CONNECTED = 1
WLAN_AVAILABLE_NETWORK_HAS_PROFILE = 2

WLAN_AVAILABLE_NETWORK_INCLUDE_ALL_ADHOC_PROFILES = 0x00000001
WLAN_AVAILABLE_NETWORK_INCLUDE_ALL_MANUAL_HIDDEN_PROFILES = 0x00000002

class DOT11_SSID(Structure):
    _fields_ = [
        ("SSIDLength", c_ulong),
        ("SSID", c_char * DOT11_SSID_MAX_LENGTH)
        ]

class WLAN_AVAILABLE_NETWORK(Structure):
    _fields_ = [
        ("ProfileName", c_wchar * 256),
        ("dot11Ssid", DOT11_SSID),
        ("dot11BssType", DOT11_BSS_TYPE),
        ("NumberOfBssids", c_ulong),
        ("NetworkConnectable", c_bool),
        ("wlanNotConnectableReason", WLAN_REASON_CODE),
        ("NumberOfPhyTypes", c_ulong),
        ("dot11PhyTypes", DOT11_PHY_TYPE * WLAN_MAX_PHY_TYPE_NUMBER),
        ("MorePhyTypes", c_bool),
        ("wlanSignalQuality", c_ulong),
        ("SecurityEnabled", c_bool),
        ("dot11DefaultAuthAlgorithm", DOT11_AUTH_ALGORITHM),
        ("dot11DefaultCipherAlgorithm", DOT11_CIPHER_ALGORITHM),
        ("Flags", DWORD),
        ("Reserved", DWORD)
        ]

class WLAN_AVAILABLE_NETWORK_LIST(Structure):
    _fields_ = [
        ("NumberOfItems", DWORD),
        ("Index", DWORD),
        ("Network", WLAN_AVAILABLE_NETWORK * 1)
        ]

WlanOpenHandle = wlanapi.WlanOpenHandle
WlanOpenHandle.argtypes = (DWORD, c_void_p, POINTER(DWORD), POINTER(HANDLE))
WlanOpenHandle.restype = DWORD

WlanEnumInterfaces = wlanapi.WlanEnumInterfaces
WlanEnumInterfaces.argtypes = (HANDLE, c_void_p, 
                               POINTER(POINTER(WLAN_INTERFACE_INFO_LIST)))
WlanEnumInterfaces.restype = DWORD

WlanGetAvailableNetworkList = wlanapi.WlanGetAvailableNetworkList
WlanGetAvailableNetworkList.argtypes = (HANDLE, POINTER(GUID), DWORD, c_void_p, 
                                        POINTER(POINTER(WLAN_AVAILABLE_NETWORK_LIST)))
WlanGetAvailableNetworkList.restype = DWORD

WlanFreeMemory = wlanapi.WlanFreeMemory
WlanFreeMemory.argtypes = [c_void_p]


if __name__ == '__main__':
    NegotiatedVersion = DWORD()
    ClientHandle = HANDLE()
    ret = WlanOpenHandle(1, None, byref(NegotiatedVersion), byref(ClientHandle))
    if ret != ERROR_SUCCESS:
        exit(FormatError(ret))

    # find all wireless network interfaces
    pInterfaceList = pointer(WLAN_INTERFACE_INFO_LIST())
    ret = WlanEnumInterfaces(ClientHandle, None, byref(pInterfaceList))
    if ret != ERROR_SUCCESS:
        exit(FormatError(ret))

    try:
        ifaces = customresize(pInterfaceList.contents.InterfaceInfo,
                              pInterfaceList.contents.NumberOfItems)
        # find each available network for each interface
        for iface in ifaces:
            print("Interface: {}".format(iface.strInterfaceDescription))
            pAvailableNetworkList = pointer(WLAN_AVAILABLE_NETWORK_LIST())
            ret = WlanGetAvailableNetworkList(ClientHandle, 
                                        byref(iface.InterfaceGuid),
                                        0,
                                        None,
                                        byref(pAvailableNetworkList))
            if ret != ERROR_SUCCESS:
                exit(FormatError(ret))
            try:
                avail_net_list = pAvailableNetworkList.contents
                networks = customresize(avail_net_list.Network, 
                                        avail_net_list.NumberOfItems)
                for network in networks:
                    print("SSID: {}, quality: {:2d}%".format(
                        network.dot11Ssid.SSID[:network.dot11Ssid.SSIDLength].decode(),
                        network.wlanSignalQuality))
            finally:
                WlanFreeMemory(pAvailableNetworkList)
    finally:
        WlanFreeMemory(pInterfaceList)

On linux, you have a couple of choices:

The standard options is to parse the output of iwlist -scan. However, if you are currently connected to a wlan and not running as root, it only returns the currently connected wlan.

If you need more than this, the best way is to query the wireless manager daemon. On modern, linuxes, this is usually NetworkManager, although wicd is becoming more popular. Both of these managers can be queried using dbus. Unless you can control what the clients have on their systems, you might need to support both of these options, or at least one option and have a fallback for iwlist.