[LOGSTASH] - Plugin input-udp and message charset


I have a an issue with the message charset received from the input-udp plugin.
A raw trace taken using tcpdmp command on linux show the message of the UDP packat like this:
Data: 8689630446410580020000001f46e00000000000000000

BUT on Logstash/Elasticsearch/Kibana discover menu, the message is the following:

I see no error message on the logstash-plain.log file.

Configuration tried:

input {

port => 7979
tags => ["nbiot","udp"]
#codec => json
codec => plain { charset => "UTF-8" }
#codec => plain { charset => "ISO-8859-1" }
#codec => plain { charset => "locale" }
#codec => line { charset => "ISO-8859-1" }


Question: I don't see the charset value 'raw', how to display the raw data as seen in the wireshark/tcpdump trace ? This is Logstash that interpret the message differently.

FYI, same issue as the following post unsolved: