How can long range forces be described in string theory?

Perturbative string theory interactions are modeled as strings coming into direct contact and then joining, or one string splitting apart. But what is the right way to think about long range or inverse square interactions using only the basic conceptual building blocks of string theory?

For example, if we wanted to be extremely pedantic and describe the orbit of Earth around the Sun in the language of perturbative string theory, can we say that the (strings comprising) each body are exchanging virtual gravitons/off shell gravitational excitations? Does such a concept of virtual strings (or any way of talking about anything off shell) even make sense when we are not working with the underpinning of spacetime filling fields, and there is no object to "host" the off shell states? If this is indeed not possible, how do we explain this without just going into a QFT limit and thereby using different concepts?

In the case of gauge interactions between open strings attached to branes, I believe this question has a natural answer. We can say that the long range interactions are mediated by the Born-Infeld theory on the brane itself. But when closed strings are involved, either gauge interactions in a heterotic theory or for gravity generally, I don't know what "runs between" massive or charged strings, so as to permit a local account of long range interactions in this manner.