Not the only channel
Dreams are only one way that the unconscious communicates with us. Other ways that come to mind are: free association (as used in Freudian analysis, for example), embarrassing mistakes (Freudian slips), bad habits, fantasies, creative efforts, handwriting, projections, tunes that stay in our minds, things we laugh at or are angered by, synchronistic phenomena, body language and bodily symptoms. With reflection, you can no doubt come up with many more.