Or, "the packet is sent from the client to the server, and it ...." I see this a lot in technical writing where the writer is explaining a flow of code or data, and is very well aware of the antecedent of it - but the reader now has to guess, read ahead, perhaps discover they were wrong, revert their mental model, and make a different guess. JRY - Just repeat yourself. Be unambiguous. Use whatever word would have been the antecedent of the pronoun, and let clarity shine thru.