conversion to analog first and sampling it on a PC. Or, even a real time share over the internet to a
friend!
Networking Background
The network streams are based on UDP. This means that they are connection-less, and can be
captured off the network by the addressed node. UDP does not guarantee delivery, so it may be
possible that packets get lost. However, on a local network this usually does not happen.
Aside from its simplicity, UDP has another advantage: it can be used to send data to multiple
receivers at once. This is called ‘multicast’. The Ultimate is capable of sending the datastreams in
unicast mode (to one specific IP address), in multicast mode (to a multicast IP address), or in
broadcast mode. When the stream is transmitted in multicast mode, the receiver needs to ‘join’ the
multicast group. Note that this will only work when the switch supports IGMP snooping, otherwise
the switch will broadcast the data over all of its network ports; thus treating the packets as broadcast
packets.
When the switch supports IGMP snooping, it will ‘see’ the network packet that is generated by the
client who wants to receive the stream when it joins the multicast group. Such a request is sent
using the IGMP protocol. Once the switch ‘sees’ this packet, it will enable the transmission of the
requested stream to the physical port on the switch that requested the data (the port the PC is
connected to). No other ports will receive the data, so the network is not flooded.
Unicast Example
When your switch does not support IGMP snooping, the use of unicast is recommended. Especially
when there are other users of your local network, that are behind WiFi links, it is not recommended
to flood the network and get angry looks from everyone else in your household.
Unicast is the simplest form. Let’s say your PC is at 192.168.0.100; either statically configured or
obtained by DHCP, and your Ultimate has the IP address 192.168.0.64; again either statically
configured or obtained from the DHCP server. You can then simply instruct the ultimate to stream
the data to IP address 192.168.0.100.
The receiving software will open a socket, listening to a specific UDP port number. It is necessary
to send the stream to this specific UDP port number, otherwise the stream cannot be received.
Multicast Example
When using multicast, a specific range of IP addresses is used for transmission: 224.0.0.0 to
239.255.255.255. Some of these addresses are reserved for a specific type of communication, like
IGMP, MDNS, and such.
Let’s say the Ultimate is configured to send the stream to 239.0.1.64. This is in the free range for
multicast on the local network (LAN). The PC application starts by telling the network
infrastructure and its own routing tables that it wants to listen to 239.0.1.64. From that moment on,
To Next Page
Loading...