Refs #20343: Add tcp documentation clarifications

Signed-off-by: Jesus Perez <jesusperez@eprosima.com>

Author: jepemi

docs/rst/user_manual/configuration.rst

@@ -535,7 +535,7 @@ An Address is defined by:
 
 * *IP*: IP of the host (public IP in case of WAN communication).
 * *Port*: Port where the Participant is listening.
-* *External Port*: Public port accessible for external entities (only for TCP).
+* *External Port*: Public port accessible for external entities (only for TCP listening-addresses).
 * *Transport Protocol*: ``UDP`` or ``TCP``.
   If it is not set, it would be chosen by default depending on the Participant Kind.
 * *IP version*: ``v4`` or ``v6``.
@@ -567,10 +567,12 @@ External Port
 -------------
 
 External port is used to configure a Server (Discovery Server or Initial Peers) that runs under a NAT and uses
-TCP transport.
+TCP transport. It is not needed for LAN cases.
 This value could be set in a TCP listening address to differentiate the public and the internal port.
 **In case this value is not set, the external port is considered to be the same as the internal one.**
 If both ports coincide, external and internal port in the network router port forwarding rules must coincide.
+Client's port must match the server's external port unless server's external port is not set, in which case it
+should match the server's port.
 For more information, check section :ref:`user_manual_wan_configuration_nat_traversal_port_forwarding_external_port`.
 
 

docs/rst/user_manual/wan_configuration.rst

@@ -40,17 +40,19 @@ Most network routers support a graphical interface where port forwarding could b
 External port
 ^^^^^^^^^^^^^
 
-In order to configure the |ddsrouter| to connect under a NAT, two ports must be taken into account.
-The internal port (a.k.a. ``port``) is the one that the host of the |ddsrouter| will use to open a socket and
-to receive information.
+In order to configure a |ddsrouter| Server that runs under a NAT and uses TCP transport, two ports must be
+taken into account. The internal port (a.k.a. ``port``) is the one that the host of the |ddsrouter| will use
+to open a socket and to receive information.
 The external port (:code:`external-port`) references the public port meant for other entities to be able
 to locate this |ddsrouter|.
 Setting the external port is useful so the network router port forwarding could redirect from a public port
 to a different value of internal host port.
+Client's port must match the server's external port unless server's external port is not set, in which case it
+should match the server's port.
 
 .. note::
 
-    External port configuration is not mandatory. If not set the internal and the external port must coincide
+    External port configuration is not mandatory. If not set, the internal and the external port must coincide
     in the network router port forwarding rules.
 
 .. warning::