proxy.json

{
	"vehicles": {
		"IMEI1":"host1",
		"IMEI2":"host2"
	},
	"servers": {
		"host1":{
			"host":"tcp.host1.com",
			"port":8081
		},
    "host2":{
      "host":"tcp.host2.com",
      "port":8080
    }
	}
}

proxy.py

#!/usr/bin/python3
#simple bidirectional python proxy. Written for KUHMUTE LLC.
#Scott Spitler II, SS Kuhmtue LLC. 2019
#MIT License

import socket
import select
import time
import sys
import json

#Changing the delay will allow for more bandwidth/performance at the cost of CPU and network
buffer_size = 4096
delay = 0.0001
forward_to = ('tcp.defaulthost.com', 8080) #default forward location if not in proxy dict
proxyList = {}

class Forward:
    def __init__(self):
        self.forward = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    def start(self, host, port):
        try:
            self.forward.connect((host, port))
            return self.forward
        except Exception as e:
            print(str(e))
            return False

class TheServer:
    input_list = []
    channel = {}

    def __init__(self, host, port):
        self.server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.server.bind((host, port))
        self.server.listen(200)

    def main_loop(self):
        self.input_list.append(self.server)
        while 1:
            time.sleep(delay)
            ss = select.select
            inputready, outputready, exceptready = ss(self.input_list, [], [])
            for self.s in inputready:
                if self.s == self.server:
                    self.on_accept()
                    break
                self.data = self.s.recv(buffer_size)
                if len(self.data) == 0:
                    self.on_close()
                    break
                else:
                    self.on_recv()

    def on_accept(self):
        proxyHost = forward_to[0]
        proxyPort = forward_to[1]

        clientsock, clientaddr = self.server.accept()

        data = clientsock.recv(buffer_size)
        datum = data.decode("utf-8").rstrip()
        cmds = [x.strip() for x in datum[:-1].split(',')]
        print("COMMANDS ON ACCEPT: "+str(cmds))
        if len(cmds) <= 3:
            print("empty message")
        else:
          if cmds[3] == "Q0" :
              #search for the matching pair
              proxyHost, proxyPort = locateProxy(cmds[2])

        forward = Forward().start(proxyHost, proxyPort)

        if forward:
            print(str(clientaddr) + "has connected")
            self.input_list.append(clientsock)
            self.input_list.append(forward)
            self.channel[clientsock] = forward
            self.channel[forward] = clientsock
        else:
            print("Can't establish connection with remote server.")
            print("closing connection to remote server...")
            clientsock.close()

    def on_close(self):
        print("has disconnected")

        self.input_list.remove(self.s)
        self.input_list.remove(self.channel[self.s])
        out = self.channel[self.s]
        self.channel[out].close()
        self.channel[self.s].close()
        del self.channel[out]
        del self.channel[self.s]

    def on_recv(self):
        data = self.data
        datum = self.data.decode("utf-8").rstrip()
        cmds = [x.strip() for x in datum[:-1].split(',')]

        dispatchMiddleware(cmds)

        print(str(data))
        self.channel[self.s].send(data)

def dispatchMiddleware(cmds):
    imei = cmds[2]
    cmd = cmds[3]

    if cmd == 'Q0':
        #append to log file
        with open("vehicles.txt", "a") as logFile:
            logFile.write(imei + '\n')
            logFile.close()

def locateProxy(imei):
    #perform the proxy pass here.

    proxyList = loadProxyOpts()
    #print(str(json.dumps(proxyList)))
    #print(str(proxyList['vehicles']))
    if imei not in proxyList['vehicles']:
        #there is no proxy for this imei number
        print("using default proxy for this vehicle")
        return forward_to[0], forward_to[1]
    else:
        print("locating proxy in list for: "+ str(imei))
        proxyId = proxyList['vehicles'][imei]
        proxyHost = proxyList['servers'][proxyId]
        return proxyHost['host'], proxyHost['port']

def loadProxyOpts():
    with open('proxy.json', 'r') as proxyFile:
        proxyList = json.load(proxyFile)
        print("loaded proxy")
        proxyFile.close()
        return proxyList

if __name__ == '__main__':

    server = TheServer('0.0.0.0', 12233)

    try:
        loadProxyOpts()
        server.main_loop()
    except KeyboardInterrupt:
        print("Ctrl C - Stopping the server....")
        sys.exit(1)