Update TCP/UDP docs

Author: nseidle

docs/img/Terminal/SparkFun RTK Everywhere - TCP-UDP Menu.png

@@ -20,36 +20,45 @@ Compatibility Icons
 
 NMEA data is generally consumed by a GIS application or Data Collector. These messages can be transmitted over a variety of transport methods. This section focuses on the delivery of NMEA messages via TCP and UDP.
 
-<figure markdown>
-![TCP/UDP Menu showing various TCP/UDP Client and Server options](./img/Terminal/SparkFun RTK Everywhere - TCP-UDP Menu.png)
-<figcaption markdown>
-TCP/UDP Menu showing various Client and Server options
-</figcaption>
-</figure>
+<p align="center">
+  <img src="img/Terminal/SparkFun RTK Everywhere - TCP-UDP Menu.png" alt="TCP/UDP Menu showing various Client and Server options">
+</p>
 
-## TCP Client and Server
+*<p align="center">TCP/UDP Menu showing various Client and Server options</p>*
+
+<p align="center">
+  <img src="img/WiFi Config/SparkFun RTK Config - TCP Port.png" alt="TCP/UDP settings using Web Config">
+</p>
 
-The RTK device supports connection over TCP. The TCP Client sits on top of the network layer (WiFi or Ethernet) and sends position data to one or more computers or cell phones for display. Some Data Collector software (such as [Vespucci](gis_software.md#vespucci)) requires that the SparkFun RTK device connect as a TCP Client. Other software (such as [QGIS](gis_software.md#qgis)) requires that the SparkFun RTK device acts as a TCP Server. Both are supported.
+*<p align="center">TCP/UDP settings using Web Config</p>*
 
-!!! note
-	Currently for WiFi: TCP is only supported while connected to local WiFi, not AP mode. This means the device will need to be connected to a WiFi network, such as a mobile hotspot, before TCP connections can occur.
+## TCP Client and Server
 
-<figure markdown>
-![TCP Port Entry](./img/WiFi%20Config/SparkFun%20RTK%20Config%20-%20TCP%20Port.png)
-<figcaption markdown>
-</figcaption>
-</figure>
+The RTK device supports connection over TCP. The TCP Client sits on top of the network layer (WiFi in general, and Ethernet/Cellular on the EVK) and sends position data to one or more computers or cell phones for display. Some Data Collector software (such as [Vespucci](gis_software.md#vespucci)) requires that the SparkFun RTK device connect as a TCP Client. Other software (such as [QGIS](gis_software.md#qgis)) requires that the SparkFun RTK device acts as a TCP Server. Both are supported.
 
 If either Client or Server is enabled, a port can be designated. By default, the port is 2947 (registered as [*GPS Daemon request/response*](https://tcp-udp-ports.com/port-2948.htm)) but any port 0 to 65535 is supported.
 
-<figure markdown>
-![Ethernet TCP Client connection](./img/Terminal/TCP_Client.gif)
-<figcaption markdown>
-</figcaption>
-</figure>
 
-The above animation was generated using [TCP_Server.py](https://github.com/sparkfun/SparkFun_RTK_Everywhere_Firmware/blob/main/Firmware/Tools/TCP_Server.py).
+<p align="center">
+  <img src="img/Terminal/TCP_Client.gif" alt="Ethernet TCP Client connection">
+</p>
+
+*<p align="center">Ethernet TCP Client connection</p>*
+
+The above animation was generated using [TCP_Server.py](https://github.com/sparkfun/SparkFun_RTK_Everywhere_Firmware/blob/main/Firmware/Tools/TCP_Server.py) and demonstrates connecting to an RTK device over TCP from a desktop.
 
 ## UDP Server
 
-NMEA messages can also be broadcast via UDP on Ethernet and WiFi, rather than TCP. If enabled, the UDP Server will begin broadcasting NMEA data over the specific port (default 10110).
+NMEA messages can also be broadcast via UDP rather than TCP. If enabled, the UDP Server will begin broadcasting NMEA data over the specific port (default 10110).
+
+## NTRIP Caster
+
+If enabled, incoming TCP connections will be answered as if the device is an NTRIP Caster and return a mount table with only one mount point. In this mode NTRIP Clients can connect directly to the RTK device without the need for a 3rd party NTRIP Caster such as RTK2Go or Emlid. This is most often used when a base RTK device is in AP or WiFi Station mode, and a rover is connected to a cell phone that is on the same WiFi network. A GIS app can then use its built in NTRIP Client to connect to the base's NTRIP Caster.
+
+## MDNS
+
+Multicast DNS allows other devices on the same network to discover this device using 'rtk.local' as its address. When MDNS is enabled, and the RTK device is acting in WiFi AP mode for configuration, typing 'rtk.local' into a browser will connect that browser to the RTK device without having to know or type in the full IP address.
+
+## Broadcast TCP/UDP over WiFi or AP
+
+TCP Server and UDP Server can connect over a local WiFi network, or by becoming an Access Point (hosting its own WiFi network) that client devices can connect to. Use option **a** to select between the type of WiFi to use for TCP/UDP Server broadcasting.