A message was sent to a channel

Facts

Works with

RTMEvents API
{
	"type": "message",
	"subtype": "group_join",
	"ts": "1358877458.000011",
	"user": "U2147483828",
	"text": "<@U2147483828|cal> has joined the group"
}

A group_join message is sent when a member joins a private group.

If the user was invited, the message will include an inviter property containing the user ID of the inviting user.