diff --git a/README.md b/README.md
index cf0a4b56..8d75a422 100644
--- a/README.md
+++ b/README.md
@@ -126,7 +126,7 @@ The relay is needed to staple the parallel incoming and outgoing connections. By
 $ croc relay
 ```
 
-Make sure to open up TCP ports (see `croc relay --help` for which ports to open). 
+By default it uses TCP ports 9009-9013. Make sure to open those up. You can customized the ports (e.g. `croc relay --ports 1111,1112`), but you must have a minimum of **2** ports for the relay. The first port is for communication and the subsequent ports are used for the multiplexed data transfer.
 
 You can send files using your relay by entering `--relay` to change the relay that you are using if you want to custom host your own.
 
@@ -134,6 +134,8 @@ You can send files using your relay by entering `--relay` to change the relay th
 $ croc --relay "myrelay.example.com:9009" send [filename]
 ```
 
+Note, when sending, you only need to include the first port (the communication port). The subsequent ports for data transfer will be transmitted back to the user from the relay.
+
 #### Self-host relay (docker)
 
 If it's easier you can also run a relay with Docker: