Question

I want to get packages from a network using TCP/IP as a client.

With …

connect((TCP_IP, TCP_PORT))

… I can change the port of the peer address. But I change the port of my local computer?

EDIT: I want to use a network card with four ports. The network card is connected to a measurement device which sends a lot of data. How can I see where the data goes? How can I distinguish between this four ports?

Answer 1

Assume you have a socket named sock… use socket.bind()

import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
DESTINATION_ADDR = '1.1.1.1'
SOURCE_PORT, DESTINATION_PORT = 31415, 80
sock.bind(('0.0.0.0', SOURCE_PORT))
sock.connect((DESTINATION_ADDR, DESTINATION_PORT))

Now I run tshark (text wireshark) to see my traffic on that interface…

[mpenning@Bucksnort ~]$ sudo tshark -i eth0 tcp and port 31415
Capturing on eth0
  0.000000 24.19.161.6 -> 1.1.1.1      TCP 31415 > http [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=4228124209 TSER=0 WS=6
 12.000009 24.19.161.6 -> 1.1.1.1      TCP 31415 > http [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=4228127209 TSER=0 WS=6
 36.000010 24.19.161.6 -> 1.1.1.1      TCP 31415 > http [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=4228133209 TSER=0 WS=6