Packets sent with scapy don't arrive and can't be sniffed

Question

I have a recurring problem where packets I send with scapy don't arrive. I tried to sniff them using scapy and wireshark, but they don't get sniffed. It's as if they weren't sent, but the script sending them displays the "sent 1 packet" message.

I looked it up and found this similar question that the problem might be that the packet is sent to the wrong interface. this seems likely, because my scapy's default iface is set to "eth0", and I sniff on my wifi connection. If this is really the problem, how do i set scapy to send & sniff on the wifi connection?

code example:

from scapy.all import *

message = raw_input("enter your message:")

for c in message:
    packet = Ether() / IP(dst = "127.0.0.1") / UDP(sport = 4001, dport = ord(c))
    send(packet)

raw_input()

In this script is supposed to send a message to a server by sending empty UDP packets to ports signifying the letters. The script runs fine, I just don't get any packets on my "server", and the packet this script supposedly sends cannot be sniffed.

EDIT: my os is windows 8.1

RyPeck RyPeck · Accepted Answer · 2015-07-11T15:35:09

The destination for your packet is 127.0.0.1 which falls under the network range for the loopback interface on your system. You could listen and send on this interface (with the aforementioned address) if you are using the same computer (but a separate process) for sniffing.

You will need to send your packet to the address of your WiFi interface on the computer you are sniffing on.

You'll also want to ensure that your firewall (if you have one running) isn't blocking the connection.

That's just the beginning of the troubleshooting process of what can be going wrong. If you are just looking to test basic Scapy - I suggest using the loopback interface on your machine to test.

Packets sent with scapy don't arrive and can't be sniffed

2 Answers