Our main assumption is that it is possible and desirable to learn while communicating and also that the most effective learning is collaboratively constructed. Thus, we describe the linguistic-pragmatic behaviours involving strategies concerning negotiation of form and meaning within a group of students who are learning Portuguese as a Second Language (PL2). The theoretical and methodological framework includes studies in Second Language Acquisition (SLA), in Applied Linguistics, in Interactional Analysis, in Language Didactics and Computer Assisted Language Learning (CALL). It is under this scope that we analyse the collected data, which consist of interaction events taking place in a chat as a PL2 classroom task. he analysis suggests that: (i) the properties of the exolanguage communication, such as the selection of communication and learning strategies are still working in the interaction under the written form in the chat; (ii) the asymmetry between the participants is a catalytic factor for collaboration and knowledge construction. Asymmetry acts, then, as a counterpart to the top-down teacher-student relationship typical in classroom face-to- face discussions; (iii)taking account of the three major Swain´s functions - Hypothesis Testing, Metalinguistic and Noticing - guiding strategies selection, there is a relationship between these functions, the negotiation type, and the participants´ proficiency in the target language; (iv) the use of chat becomes an open window for the linguistic production as well as for pragmatic uses in PL2. The task of chat sheds light on the process of knowledge construction in Second Language (L2), which is simultaneously individual and collaborative.