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?