diff --git a/src/aleph/sdk/client.py b/src/aleph/sdk/client.py
index bdd78c23..9877d716 100644
--- a/src/aleph/sdk/client.py
+++ b/src/aleph/sdk/client.py
@@ -54,7 +54,7 @@
     MultipleMessagesError,
 )
 from .models import MessagesResponse
-from .utils import get_message_type_value
+from .utils import check_unix_socket_valid, get_message_type_value
 
 logger = logging.getLogger(__name__)
 
@@ -94,14 +94,14 @@ def func_caller(*args, **kwargs):
 
 
 async def run_async_watcher(
-    *args, output_queue: queue.Queue, api_server: str, **kwargs
+    *args, output_queue: queue.Queue, api_server: Optional[str], **kwargs
 ):
     async with AlephClient(api_server=api_server) as session:
         async for message in session.watch_messages(*args, **kwargs):
             output_queue.put(message)
 
 
-def watcher_thread(output_queue: queue.Queue, api_server: str, args, kwargs):
+def watcher_thread(output_queue: queue.Queue, api_server: Optional[str], args, kwargs):
     asyncio.run(
         run_async_watcher(
             output_queue=output_queue, api_server=api_server, *args, **kwargs
@@ -443,9 +443,39 @@ class AlephClient:
     api_server: str
     http_session: aiohttp.ClientSession
 
-    def __init__(self, api_server: str):
-        self.api_server = api_server
-        self.http_session = aiohttp.ClientSession(base_url=api_server)
+    def __init__(
+        self,
+        api_server: Optional[str],
+        api_unix_socket: Optional[str] = None,
+        allow_unix_sockets: bool = True,
+        timeout: Optional[aiohttp.ClientTimeout] = None,
+    ):
+        """AlephClient can use HTTP(S) or HTTP over Unix sockets.
+        Unix sockets are used when running inside a virtual machine,
+        and can be shared across containers in a more secure way than TCP ports.
+        """
+        self.api_server = api_server or settings.API_HOST
+        if not self.api_server:
+            raise ValueError("Missing API host")
+
+        unix_socket_path = api_unix_socket or settings.API_UNIX_SOCKET
+        if unix_socket_path and allow_unix_sockets:
+            check_unix_socket_valid(unix_socket_path)
+            connector = aiohttp.UnixConnector(path=unix_socket_path)
+        else:
+            connector = None
+
+        # ClientSession timeout defaults to a private sentinel object and may not be None.
+        self.http_session = (
+            aiohttp.ClientSession(
+                base_url=self.api_server, connector=connector, timeout=timeout
+            )
+            if timeout
+            else aiohttp.ClientSession(
+                base_url=self.api_server,
+                connector=connector,
+            )
+        )
 
     def __enter__(self) -> UserSessionSync:
         return UserSessionSync(async_session=self)
@@ -825,8 +855,20 @@ class AuthenticatedAlephClient(AlephClient):
         "channel",
     }
 
-    def __init__(self, account: Account, api_server: str):
-        super().__init__(api_server=api_server)
+    def __init__(
+        self,
+        account: Account,
+        api_server: Optional[str],
+        api_unix_socket: Optional[str] = None,
+        allow_unix_sockets: bool = True,
+        timeout: Optional[aiohttp.ClientTimeout] = None,
+    ):
+        super().__init__(
+            api_server=api_server,
+            api_unix_socket=api_unix_socket,
+            allow_unix_sockets=allow_unix_sockets,
+            timeout=timeout,
+        )
         self.account = account
 
     def __enter__(self) -> "AuthenticatedUserSessionSync":
diff --git a/src/aleph/sdk/utils.py b/src/aleph/sdk/utils.py
index 4290bcf6..fdbf6095 100644
--- a/src/aleph/sdk/utils.py
+++ b/src/aleph/sdk/utils.py
@@ -1,3 +1,4 @@
+import errno
 import logging
 import os
 from pathlib import Path
@@ -59,3 +60,19 @@ def get_message_type_value(message_type: Type[GenericMessage]) -> MessageType:
     """Returns the value of the 'type' field of a message type class."""
     type_literal = message_type.__annotations__["type"]
     return type_literal.__args__[0]  # Get the value from a Literal
+
+
+def check_unix_socket_valid(unix_socket_path: str) -> bool:
+    """Check that a unix socket exists at the given path, or raise a FileNotFoundError."""
+    path = Path(unix_socket_path)
+    if not path.exists():
+        raise FileNotFoundError(
+            errno.ENOENT, os.strerror(errno.ENOENT), unix_socket_path
+        )
+    if not path.is_socket():
+        raise FileNotFoundError(
+            errno.ENOTSOCK,
+            os.strerror(errno.ENOENT),
+            unix_socket_path,
+        )
+    return True