Provided are a method, system, and program for transferring data between an initiator node and target node. A request is received conforming to a first data transfer protocol at the initiator node to transmit to the target node. A reference to a memory location is obtained to use to transfer the request to the target node. At least one function is called that executes in a user address space of the initiator node, wherein the initiator node includes a kernel address space and the user address space. The at least one function executing in the user address space interfaces with an adaptor to transmit the request and reference to the memory location to the target node using a second data transfer protocol.