Re: Communicating with WSJT-X over UDP #udp

Bill Somerville

On 22/11/2020 14:08, Philip Rose via wrote:

Thanks, Bill.


I wasn’t sure I understood that there could be more than one server. You say ‘interoperating’, surely a server would only respond to UDPs addressed to it. Or can an application be server and client? Or several servers having the same address? What other applications are likely to be servers? Do you expect people to have multiple loggers? What other sort of applications would be servers?


73 Phil GM3ZZA.

Hi Phil,

one of the reasons why WSJT-X uses UDP for interoperation with other applications is because that allows a many-to-many topology without having to use different service ports for each server. This is enabled by using multicast IP, a server can bind a service port using SO_REUSEADDR and join a multicast group to express an interest in datagrams sent to that group. The networking infrastructure will deliver such datagrams, by copying them if necessary (multicast is the only networking protocol where packets can be copied) so that every member of a multicast group can receive their own copy of each datagram.

There are already several applications that can run in parallel as servers interoperating with WSJT-X instances. JTAlert, Gridtracker, and WSJT-X Monitor for example. They often do have some overlap in functionality, but that's fine so long as only one of them is responsible for logging QSOs in any main station log.


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