-/* Opens a non-blocking TCP socket, binds to 'target', and listens for incoming
- * connections. 'target' should be a string in the format "[<port>][:<ip>]",
- * where both <port> and <ip> are optional. If <port> is omitted, it defaults
- * to 'default_port'; if <ip> is omitted it defaults to the wildcard IP
- * address.
+/* Opens a non-blocking IPv4 socket of the specified 'style', binds to
+ * 'target', and listens for incoming connections. 'target' should be a string
+ * in the format "[<port>][:<ip>]":
+ *
+ * - If 'default_port' is -1, then <port> is required. Otherwise, if
+ * <port> is omitted, then 'default_port' is used instead.
+ *
+ * - If <port> (or 'default_port', if used) is 0, then no port is bound
+ * and the TCP/IP stack will select a port.