Ahh ok so you are trying to read syslog then see here. Your config is not correct
Please look at the docs
The samples are right there
filebeat.inputs:
- type: syslog
format: rfc3164
protocol.udp:
host: "localhost:9000"
filebeat.inputs:
- type: syslog
format: rfc5424
protocol.tcp:
host: "localhost:9000"
filebeat.inputs:
- type: syslog
format: auto
protocol.unix:
path: "/path/to/syslog.sock"