I want to capture the wifi traffic from my wireless card, so what i have to do and are there tools for that? I know that there is aircrack-ng and airodump, but these tools need a extra wireless adapter and is their a possibility to capture wifi traffic without buying a extra wifi adapter?
Aircrack-ng, Fern, and other sectools for wifi pen testing are a capture and correlate type application. If you do not need automated correlation and are simply interested in traffic capture out your own Ethernet interface you can capture with wireshark, tcpdump, netcat, ettercap, net hogs, scapy, cloudshark, packetyzer and many many more. They all have the ability to capture wifi traffic on the local interface: see this wiki for tuts on how to capture using shark for Windows:
This has details of how to setup capture for LAN out of local device interface and for capture self generated (local host) non Ethernet traffic from local host. (Use this to test if you are capturing). Hope this helps.
arjun@arjun-Precision-T1600:~$ iw phy | grep -A 8 "Supported interface modes Supported interface modes * IBSS * managed * AP * AP/VLAN * monitor * mesh point * P2P-client * P2P-GO
If you get monitor mode in the list, you don't need to buy extra hardware.
Just put your card in monitor mode:
$ iwconfig <wireless_card> mode monitor
Wireshark to the interface:
$ wireshark -i <wireless_card>