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CommView for WiFi provides a simple TCP/IP interface that allows
you to process packets captured by CommView for WiFi using your own
application in real time. Starting with version 5.0, you may also
use this interface for sending packets (similar to the Packet
Generator function in CommView).
How It Works
CommView for WiFi should be launched with a special command-line
argument, "MIRROR", that tells the program to mirror captured
packets to an IP address and TCP port of your choice.
Examples:
CV.EXE mirror:127.0.0.1:5555 // mirrors packets to the
loopback address, TCP port 5555
CV.EXE mirror:192.169.0.2:10200 // mirrors packets to
192.169.0.2, TCP port 10200
When CommView for WiFi is launched with a switch like this, it
tries to establish a TCP session by connecting to the specified IP
address and port number. It means that you should already have your
application running and listening on the specified port. If
CommView for WiFi fails to establish a connection, it will keep on
trying to connect every 15 seconds. The same happens if the
connection is broken: CommView for WiFi will try to re-establish it
every 15 seconds. If the connection is successfully established,
CommView for WiFi sends the packets it captures to the specified IP
address as they arrive, in real time.
Data Format
The data is transmitted in NCFX format. Please refer to the
CommView Log Files
Format
chapter for the format description.
Sending Packets
Packets may not only be received by your application but also sent
as if you were using Packet Generator. Data can be sent to CommView
for WiFi using the same TCP connection over which you are receiving
the data. The data format is simple: You should send the packet
length (a two-byte unsigned integer in the standard little-endian
byte order) followed by the data rate index (a two-byte unsigned
integer in the standard little-endian byte order) followed by the
packet itself. Packet length should not include the four bytes that
precede the packet body. Data rate index is zero-based; it should
contain the index of the rate as shown in
the Packet Generator.
Consider the following example:
String to be sent in hex: D4
00 00 00 80 1F 02 66 C2 8E.
The length of this string is 10 bytes.
Rate to be used: 5.5 Mbps. This is the third item in the "802.11
data rate" drop-down list in the Packet Generator.
Resulting buffer to be sent: 0A
00 02 00 D4 00 00 00 80 1F 02 66 C2 8E.
If the adapter is not opened or it does not support packet
injection, the packet is silently discarded.
Sample Projects
Two simple demo applications that listen for inbound connections,
extract packets from the stream, and display raw data are
available.
·http://www.tamos.com/products/commwifi/samp_mirr_c7.zip.
This is a Visual Studio project with C++ source code.
·http://www.tamos.com/products/commwifi/samp_mirr_d7.zip.
This is a Delphi project with Pascal source code. If you want to
compile the project, you will need the popular ICS components suite
by Francois Piette, available at http://www.overbyte.be.
Bandwidth
When mirroring data to a remote computer, make sure that the link
between CommView and the computer to which the data is being
mirrored is fast enough to transfer all the data being captured. If
CommView captures 500 Kbytes/sec, and your link can handle only 50
Kbytes/sec, you'd inevitably have "traffic jams," which might
result in various problems (e.g., Winsock may just stop sending
data under some Windows versions).
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