diff --git a/src/ipc/lowlevel.cr b/src/ipc/lowlevel.cr
index 40fe824..119ef30 100644
--- a/src/ipc/lowlevel.cr
+++ b/src/ipc/lowlevel.cr
@@ -4,9 +4,10 @@ lib LibIPC
 	INFTIM = -1
 
 	enum ConnectionType
-		IPC
-		External
-		Server
+		IPC       # IO op. are handled by libipc.
+		External  # IO op. are handled by the libipc user app.
+		Server    # Should listen and accept new IPC users.
+		Switched  # IO op. are handled by callbacks.
 	end
 
 	struct Connection
@@ -88,6 +89,7 @@ lib LibIPC
 	# Context is allocated, ipcd is requested and the connection/initialisation is performed.
 	fun ipc_server_init(ctx : Ctx*, sname : LibC::Char*) : IPCError
 	fun ipc_connection(Ctx*, LibC::Char*) : IPCError
+	fun ipc_connection_switched(Ctx*, LibC::Char*) : IPCError
 
 	# Closing connections.
 	fun ipc_close(ctx : Ctx*, index : LibC::UInt64T) : IPCError
@@ -102,6 +104,7 @@ lib LibIPC
 	fun ipc_add(Ctx*, Connection*, Pollfd*) : IPCError
 	fun ipc_del(Ctx*, LibC::UInt) : IPCError
 	fun ipc_add_fd(Ctx*, LibC::Int) : IPCError
+	fun ipc_add_fd_switched(Ctx*, LibC::Int) : IPCError
 	fun ipc_del_fd(Ctx*, LibC::Int) : IPCError
 
 	# Sending a message (will wait the fd to become available for IO operations).
@@ -115,6 +118,24 @@ lib LibIPC
 	fun ipc_receive_fd (sock : LibC::Int, fd : LibC::Int*) : IPCError
 	fun ipc_provide_fd (sock : LibC::Int, fd : LibC::Int ) : IPCError
 
+	# To change the type of a fd.
+	fun ipc_ctx_fd_type(Ctx*, LibC::Int, LibIPC::ConnectionType) : IPCError
+
+	enum IPCCB
+		NoError       #
+		Closing       #
+		Error         #
+		ParsingError  #
+	end
+
+	# Changing the callbacks for switched fd.
+	# ipc_switching_callbacks: ctx, fd
+	# , enum ipccb cb_in  (fd, *ipc_message)
+	# , enum ipccb cb_out (fd, *ipc_message)
+	fun ipc_switching_callbacks(Ctx*, LibC::Int,
+		cb_in  : (LibC::Int, Pointer(LibIPC::Message)) -> LibIPC::IPCCB,
+		cb_out : (LibC::Int, Pointer(LibIPC::Message)) -> LibIPC::IPCCB) : IPCError
+
 	fun ipc_switching_add  (switch : Switchings*, fd1 : LibC::Int, fd2 : LibC::Int) # Void
 	fun ipc_switching_del  (switch : Switchings*, fd  : LibC::Int                 ) : LibC::Int
 	fun ipc_switching_get  (switch : Switchings*, fd  : LibC::Int                 ) : LibC::Int