Add a README for the UDP listener input plugin

plugins/inputs/udp_listener/README.md

@@ -0,0 +1,31 @@
+# UDP listener service input plugin
+
+The UDP listener is a service input plugin that listens for messages on a UDP
+socket and adds those messages to InfluxDB.
+The plugin expects messages in the
+[Telegraf Input Data Formats](https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md).
+
+### Configuration:
+
+This is a sample configuration for the plugin.
+
+```toml
+[[inputs.udp_listener]]
+  ## Address and port to host UDP listener on
+  service_address = ":8125"
+
+  ## Number of UDP messages allowed to queue up. Once filled, the
+  ## UDP listener will start dropping packets.
+  allowed_pending_messages = 10000
+
+  ## UDP packet size for the server to listen for. This will depend
+  ## on the size of the packets that the client is sending, which is
+  ## usually 1500 bytes.
+  udp_packet_size = 1500
+
+  ## Data format to consume. This can be "json", "influx" or "graphite"
+  ## Each data format has it's own unique set of configuration options, read
+  ## more about them here:
+  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
+  data_format = "influx"
+```