recv.2: Improve text describing recvfrom() call that is equivalent to recv()

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/recv.2

@@ -289,12 +289,10 @@ The
 call is normally used only on a
 .I connected
 socket (see
-.BR connect (2))
-and is identical to
-.BR recvfrom ()
-with a NULL
-.I src_addr
-argument.
+.BR connect (2)).
+It is equivalent to the call:
+
+    recvfrom(fd, buf, len, flags, NULL, 0));
 .\"
 .SS recvmsg()
 The