2

I don't know if it the case of network config or something is wrong with my software.

I have a device whose address is 192.168.4.83. This device is connected directly to my pc linux server, which has address 192.168.4.11.

I want to send a UDP packet from a server to the device, using python. The server is also listening for responses. I have a simple python script to do that. I send using:

    self.sendSocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    self.sendSocket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST,1)
    sock.sendSocket.send(msg,('<boradcast>', UDP_PORT))

I listen and bind to 0.0.0.0. The code is very simple: one thread is sending udp packets, the other one has while(1) loop which only receives packets.

This is the listening code:

class CUdp(threading.Thread):
    def __init__(self, log=False):
        threading.Thread.__init__(self)
        self.running = True
        self.listenSocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self.listenSocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.listenSocket.bind(("", UDP_PORT))
        self.last_time = 0
        self.now = 0
        self.log = log
    def run(self):
        global sent_time
        while(self.running):
            data, addr = self.listenSocket.recvfrom(1024) 
            if data != None:
               recv_time = time.time()
               myprint("[RECV " +  str(datetime.datetime.now()) + "] (len=" + str(len(data)) +") : " +  str(data)+"\n", self.log)

The strange thing is that, on wireshark i can see that: packet has been sent from 192.168.4.11 to 255.255.255.255, and device has responded to this packet - packet from 192.168.4.83 has been sent to 255.255.255.255. It seems, that using bind (0.0.0.0, port) does not cover 255.255.255.255. I'm lost and I have no ideas.

ifconfig is:

eth0      Link encap:Ethernet  HWaddr 2C:41:38:9B:BF:CA  
          inet addr:192.168.4.11  Bcast:192.168.4.255  Mask:255.255.255.0
          inet6 addr: fe80::2e41:38ff:fe9b:bfca/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:34 errors:0 dropped:0 overruns:0 frame:0
          TX packets:413 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:5050 (4.9 KiB)  TX bytes:26688 (26.0 KiB)
          Interrupt:17

Any clues?

BartoszKP
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JosiP
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  • Take a look at the answer here - it may help explain the behaviour: http://stackoverflow.com/a/13675919/334402? – Mick Oct 29 '13 at 23:11

1 Answers1

0

Assuming all the code is written properly, this could just be a problem with the linux firewall. You can add your ip address to iptables or you can just take down the firewall if your in a safe network environment:

/etc/init.d/iptables stop

KAJ
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