both are right, though 'est-ce que tu viens?' is more gramatically correct. Use it when writing, when speaking you can just say 'tu viens?', it sounds more natural.

At the conversational level, "tu viens?" looks fine (as long as you raise you tone when you ask). In writing, however, French usually uses either the inversion (except for asking oneself [with "je"], then it limits with only a few expressions) or putting the phrase "est-ce que" in the front (except for interrogative adverbs, like "what", "where" etc., then they need to be put before "est-ce que" ). Hence, the question can be written as, " Est-ce que tu viens? " OR " Viens-tu? " The construction of question with the term "est-ce que" is however easier to the beginners. -- Good weekend. / Bonne fin de semaine.

you have explained it very well - and it is very clear to me now :) Thanks again .. I wish that too :) . Have a good weekend !

Salut. Je te remercie beaucoup d'avoir choisi ma réponse comme la meilleure. Ça me donne une reconnaissance positive lorsque je réponds aux questions des autres membres. J'espère que nous continuons ensemble l'apprentissage des langues étrangrères.　/　Hi. I thank you very much for having chosen my answer as the best one. This gives me a positive recognition when I answer the questions of other members. I hope that together we continue the learning of foreign languages.