diff --git a/Doc/library/smtpd.rst b/Doc/library/smtpd.rst
index ebb0b30..7d6534b 100644
--- a/Doc/library/smtpd.rst
+++ b/Doc/library/smtpd.rst
@@ -23,9 +23,10 @@
 .. class:: SMTPServer(localaddr, remoteaddr)
 
    Create a new :class:`SMTPServer` object, which binds to local address
-   *localaddr*.  It will treat *remoteaddr* as an upstream SMTP relayer.  It
-   inherits from :class:`asyncore.dispatcher`, and so will insert itself into
-   :mod:`asyncore`'s event loop on instantiation.
+   *localaddr*.  It will treat *remoteaddr* as an upstream SMTP relayer.  Both
+   *localaddr* and *remoteaddr* should be a :ref:`(host, port) <host_port>`
+   tuple.  The object inherits from :class:`asyncore.dispatcher`, and so will
+   insert itself into :mod:`asyncore`'s event loop on instantiation.
 
 
    .. method:: process_message(peer, mailfrom, rcpttos, data)
diff --git a/Doc/library/socket.rst b/Doc/library/socket.rst
index 73b5d5c..aff6a2e 100644
--- a/Doc/library/socket.rst
+++ b/Doc/library/socket.rst
@@ -34,6 +34,8 @@
 files, buffer allocation on receive operations is automatic, and buffer length
 is implicit on send operations.
 
+.. _host_port:
+
 Socket addresses are represented as follows: A single string is used for the
 :const:`AF_UNIX` address family. A pair ``(host, port)`` is used for the
 :const:`AF_INET` address family, where *host* is a string representing either a