Add "default protocols" that all hosts have by default

libp2p/host/basic_host.py

@@ -1,8 +1,9 @@
 import logging
-from typing import List, Sequence
+from typing import TYPE_CHECKING, List, Sequence
 
 import multiaddr
 
+from libp2p.host.defaults import DEFAULT_HOST_PROTOCOLS
 from libp2p.host.exceptions import StreamFailure
 from libp2p.network.network_interface import INetwork
 from libp2p.network.stream.net_stream_interface import INetStream
@@ -17,6 +18,9 @@ from libp2p.typing import StreamHandlerFn, TProtocol
 
 from .host_interface import IHost
 
+if TYPE_CHECKING:
+    from collections import OrderedDict
+
 # Upon host creation, host takes in options,
 # including the list of addresses on which to listen.
 # Host then parses these options and delegates to its Network instance,
@@ -38,12 +42,16 @@ class BasicHost(IHost):
     multiselect: Multiselect
     multiselect_client: MultiselectClient
 
-    def __init__(self, network: INetwork) -> None:
+    def __init__(
+        self,
+        network: INetwork,
+        default_protocols: "OrderedDict[TProtocol, StreamHandlerFn]" = DEFAULT_HOST_PROTOCOLS,
+    ) -> None:
         self._network = network
         self._network.set_stream_handler(self._swarm_stream_handler)
         self.peerstore = self._network.peerstore
         # Protocol muxing
-        self.multiselect = Multiselect()
+        self.multiselect = Multiselect(default_protocols)
         self.multiselect_client = MultiselectClient()
 
     def get_id(self) -> ID:

libp2p/host/defaults.py

@@ -0,0 +1,7 @@
+from collections import OrderedDict
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from libp2p.typing import TProtocol, StreamHandlerFn
+
+DEFAULT_HOST_PROTOCOLS: "OrderedDict[TProtocol, StreamHandlerFn]" = OrderedDict()

libp2p/protocol_muxer/multiselect.py

@@ -19,8 +19,8 @@ class Multiselect(IMultiselectMuxer):
 
     handlers: Dict[TProtocol, StreamHandlerFn]
 
-    def __init__(self) -> None:
+    def __init__(self, default_handlers: Dict[TProtocol, StreamHandlerFn] = {}) -> None:
-        self.handlers = {}
+        self.handlers = default_handlers
 
     def add_handler(self, protocol: TProtocol, handler: StreamHandlerFn) -> None:
         """