Creating Network Packets 
Author Message
 Creating Network Packets

Hi,

    I don't know how to create a packet of data but to broadcast it's a
little bit more easier. For exemple, if your IP is 192.168.0.1 using a
subnet mask of 255.255.255.0, the broadcast address is 192.168.0.255. Most
of the time this address is used by the address resolution protocol (ARP)
and some other protocol.

    Attention, there is a pitfall here. Your message will only be heard by
the station on the same subnet. Some router will re-broadcast to other
subnet and some will not forward this address to other subnet.

    Also, you will have to use special network procedure to retrive the
frame broadcasted on the network broadcast address.

    I hope this have helped you.

Bye

Cy

Quote:

>Can anybody help me with this task.

>I need to create an application that sends a packet of of data across our
>internal network that contains a specific data structure in the main body
of
>the packet, and then another application to trap that packet, decode the
>senders MAC address from the packet, and then reply.

>1. How do I create a packet of data ?

>2. How do I then send that data as a broadcast across the network ?

>Any help, lots of help would be appreciated.

>Thanks, Graeme.



Sat, 24 Mar 2001 03:00:00 GMT  
 Creating Network Packets
Can anybody help me with this task.

I need to create an application that sends a packet of of data across our
internal network that contains a specific data structure in the main body of
the packet, and then another application to trap that packet, decode the
senders MAC address from the packet, and then reply.

1. How do I create a packet of data ?

2. How do I then send that data as a broadcast across the network ?

Any help, lots of help would be appreciated.

Thanks, Graeme.



Sun, 25 Mar 2001 03:00:00 GMT  
 Creating Network Packets
What kind of datagram do you want to send? Is it an well-known format or
something custom?

To broadcast a packet, you need to calculate the broadcast address. This is
done automatically (along with a bunch of other stuff) by my IPBandit
control. Check it out at http://members.tripod.com/SneakyWeb

Remember that a broadcast will usually only reach all computers on the same
subnet. Routers discard most broadcasts.

--
Eric Robinson

Quote:

>Can anybody help me with this task.

>I need to create an application that sends a packet of of data across our
>internal network that contains a specific data structure in the main body
of
>the packet, and then another application to trap that packet, decode the
>senders MAC address from the packet, and then reply.

>1. How do I create a packet of data ?

>2. How do I then send that data as a broadcast across the network ?

>Any help, lots of help would be appreciated.

>Thanks, Graeme.



Tue, 27 Mar 2001 03:00:00 GMT  
 Creating Network Packets
The type of packet is called , by AMD , 'Magic Packets' , for initiating the
Wake-Up-On-Lan.
According to their documentation the packet must consist of, in the exact
sequence,
SOURCE DEST MISC FF FF FF FF FF FF FF FF { 16 consecutive instances of the
destination MAC address } MISC CRC.

What the misc parts are I don't know yet but I can find out by using a
packet sniffer.
The problem I have , is how to create this packet and how to send it.

The broadcast thing isn't a problem because the computers are all the the
same room off the same hub, etc..

There is a program on the AMD site which works wonderfully, but as is
usually the case, it doesn't quite do what I want it to, hence the reason I
need to write something myself.

Graeme.
(remove NOSPAM if replying by email).



Wed, 28 Mar 2001 03:00:00 GMT  
 Creating Network Packets
Check out the discussion of using User-defined Types with Catalyst's
SocketWrench control. http://www.catalyst.com/support/tips/tip3.html

The issues discussed there apply to your question.


Quote:
>The type of packet is called , by AMD , 'Magic Packets' , for initiating
the
>Wake-Up-On-Lan.
>According to their documentation the packet must consist of, in the exact
>sequence,
>SOURCE DEST MISC FF FF FF FF FF FF FF FF { 16 consecutive instances of the
>destination MAC address } MISC CRC.

>What the misc parts are I don't know yet but I can find out by using a
>packet sniffer.
>The problem I have , is how to create this packet and how to send it.

>The broadcast thing isn't a problem because the computers are all the the
>same room off the same hub, etc..

>There is a program on the AMD site which works wonderfully, but as is
>usually the case, it doesn't quite do what I want it to, hence the reason I
>need to write something myself.

>Graeme.
>(remove NOSPAM if replying by email).



Mon, 02 Apr 2001 03:00:00 GMT  
 
 [ 5 post ] 

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