A dryer vent must exhaust to the exterior of the building AND have some kind of access for cleaning out. The exterior vent should have a back flow stop to prevent outside air from infiltrating the building.
The gasket shown below makes for an easy pipe fitting and ease of ensuring a positive overlap.
HVAC gasket from Greenskin / Pro-Flash
Things to remember:
Don't vent the dryer to the inside of the building. This messes with your ventilation and indoor air quality.
Poorly cleaned or improperly installed dryer vents are one of the biggest culprits for house fires. Make the clear out trap easy to access.