`sig
type protocol = Tcp | Udp
type mode = Socket | BiPipe
type server_error =
Unavailable_program
| Unavailable_version of (Rtypes.uint4 * Rtypes.uint4)
| Unavailable_procedure
| Garbage
| System_err
| Rpc_mismatch of (Rtypes.uint4 * Rtypes.uint4)
| Auth_bad_cred
| Auth_rejected_cred
| Auth_bad_verf
| Auth_rejected_verf
| Auth_too_weak
| Auth_invalid_resp
| Auth_failed
| RPCSEC_GSS_credproblem
| RPCSEC_GSS_ctxproblem
val string_of_server_error : Rpc.server_error -> string
exception Rpc_server of Rpc.server_error
exception Rpc_cannot_unpack of string
end`