FileBeat 1.3.1 sends logs containing json to logstash 2.4

[Jerry_Wang1 (Jerry Wang)]

My log format is a json string per each line as below.

{"level":"INFO","message":"Loading database shards","source":"UBS.Bootstrap","details":"","type":"ubs-log4net","@version":1,"host":"JERRYWANG01","@timestamp":"2019-03-16T02:36:26,292"}
{"level":"INFO","message":"1 database servers are detected","source":"UBS.Data.Sharding.ShardManager","details":"","type":"ubs-log4net","@version":1,"host":"JERRYWANG01","@timestamp":"2019-03-16T02:36:31,659"}

My Logstash 2.4 is configured with tcp input as below.

input {
    tcp {
        port => 6001
        codec => json_lines { }
    }
}

It works well when I send the log file directly to TCP port 6001.

Now I want to transfer the logs via filebeat. Because I am using an old version logstash , I choose filebeat 1.3.1

First added beat input in logstash

input {
    beats {
        port => 5044
        codec => json_lines { }
    }
}

And here is filebeat.yml

filebeat:
  prospectors:
    -
      paths:
        - C:\Users\Jerry.Wang\logs\*.log

      input_type: log


  registry_file: "C:/ProgramData/filebeat/registry"

output:

  logstash:
    # The Logstash hosts
    hosts: ["192.168.2.99:5044"]

I can see logs are transferred successfully from filebeat output, but it is not stored by logstash. What could be wrong?