locked Re: WSJT-X rc2


g4wjs
 

On 15/11/2020 21:14, HamApps Support (VK3AMA) wrote:
On 16/11/2020 7:51 am, g4wjs wrote:

you appear to be one of the users using an inappropriate multicast address that has caused this change to be made. Until a version of JTAlert is available that will receive multicast traffic on the loop-back network interface, you can restore functionality by choosing your local subnet network interface in WSJT-X "Settings->Reporting->UDP Server->Outgoing interface".

Multicast addresses in the 239.0.0.0/16 block are potentially globally routed, that is not a good choice for getting traffic to a server on the same host or your local subnet.


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73
Bill
G4WJS.

Bill,

JTAlert will work with a 224.0.0.0/16 multicast address. Try it.

From my JTAlert Help->About ...
   

Laurie,

as I explained off list, 224.0.0.1 is a special multicast address known as the "All Hosts" address. The 224.0.0.0/8 block of addresses is also special as they are never routed. 224.0.0.1 specifically (not just any 224.0.0.0/8 address) will work with the current JTAlert because every host joins that multicast group, on every network interface, automatically without the recipient application requesting membership. 224.0.0.1, the "All Hosts" multicast address, is just one member of the 224.0.0.0/24 block of 255 multicast addresses.

I think there may be some fundamental misunderstanding here about IPv4 address notation. IPv4 addresses are 32-bit numbers which are often written as a group of 4 decimal octets (representing 8-bits each), known as dotted decimal notation. IPv4 addresses are also written as groups, or subnets, where a specified number of high order bits, the prefix, are fixed and the remaining lower order bits form he membership of the subnet group. Some common subnets are:

127.0.0.0/8 - the loop-back addresses (they all start with 127., yes >16 million of them!), of which 127.0.0.1 is the most commonly used and supported.

192.168.0.0/16 - the class C private address block, they all start with 192.168. and are not normally routed.

172.16.0.0/12 - the class B private address block, they are 172.16.0.0 thru 172.31.255.255, also not normally routed.

10.0.0.0/8 - the class A private address block, they all start with 10., also not normally routed.

224.0.0.0/4 - the multicast group addresses, they are 224.0.0.0 thru 239.255.255.255.

Multicast group addresses are further subdivided, including 224.0.0.0/8 (not routed), and 239.0.0.0/24 (routing scope determined by further subdivisions and router settings, a.k.a. administratively scoped).


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73
Bill
G4WJS.

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