diff --git a/applications/anatomy.rst b/applications/anatomy.rst
index ba5185a..a93ec79 100644
--- a/applications/anatomy.rst
+++ b/applications/anatomy.rst
@@ -85,19 +85,20 @@ operation:
 The reason that this operation takes three arguments is that the socket
 interface was designed to be general enough to support any underlying
 protocol suite. Specifically, the ``domain`` argument specifies the
-protocol *family* that is going to be used: ``PF_INET`` denotes the
-Internet family, ``PF_UNIX`` denotes the Unix pipe facility, and
-``PF_PACKET`` denotes direct access to the network interface (i.e., it
-bypasses the TCP/IP protocol stack). The ``type`` argument indicates the
-semantics of the communication. ``SOCK_STREAM`` is used to denote a byte
-stream. ``SOCK_DGRAM`` is an alternative that denotes a message-oriented
-service, such as that provided by UDP. The ``protocol`` argument
-identifies the specific protocol that is going to be used. In our case,
-this argument is ``UNSPEC`` because the combination of ``PF_INET`` and
-``SOCK_STREAM`` implies TCP. Finally, the return value from ``socket``
-is a *handle* for the newly created socket—that is, an identifier by
-which we can refer to the socket in the future. It is given as an
-argument to subsequent operations on this socket.
+communication domain that is going to be used: ``AF_INET`` denotes the
+IPv4 Internet family, ``AF_UNIX`` denotes the Unix-domain socket family
+for communication between local processes, and ``AF_PACKET`` provides
+low-level access to packets at the network-device level. The ``type``
+argument indicates the semantics of the communication. ``SOCK_STREAM``
+is used to denote a byte stream. ``SOCK_DGRAM`` is an alternative that
+denotes a message-oriented service, such as that provided by UDP. The
+``protocol`` argument identifies the specific protocol that is going to
+be used. In our case, this argument is ``0``, which selects TCP as the
+default protocol for the ``AF_INET`` and ``SOCK_STREAM`` combination.
+Finally, the return value from ``socket`` is a *handle* for the newly
+created socket—that is, an identifier by which we can refer to the
+socket in the future.
+It is given as an argument to subsequent operations on this socket.
 
 The next step depends on whether you are a client or a server. On a
 server machine, the application process performs a *passive* open—the
diff --git a/resources/code/simplex-client.c b/resources/code/simplex-client.c
index 16321c1..374226a 100644
--- a/resources/code/simplex-client.c
+++ b/resources/code/simplex-client.c
@@ -48,7 +48,7 @@ main(int argc, char *argv[])
   sin.sin_port = htons(SERVER_PORT);
 
   /* active open */
-  if ((s = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
+  if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
     perror("socket");
     exit(1);
   }
diff --git a/resources/code/simplex-server.c b/resources/code/simplex-server.c
index b0fcf15..17e2299 100644
--- a/resources/code/simplex-server.c
+++ b/resources/code/simplex-server.c
@@ -39,7 +39,7 @@ main(int argc, char *argv[])
   sin.sin_port = htons(SERVER_PORT);
 
   /* setup passive open */
-  if ((s = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
+  if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
     perror("socket");
     exit(1);
   }