An NTRIP Caster is the real server element in the overall NTRIP system.   
SNIP is an NTRIP Caster.     Go to SNIP download page

An NTRIP Caster takes data from one or more data stream sources (Base Stations referred to as NTRIP Servers) and provides this data to one or more end users (often called rovers), the NTRIP Clients.  If you need to send data to more than one client at a time, or have more than one data stream, you will need a Caster.

NTRIP Servers are typically GNSS reference stations of various quality levels with a thin layer of software to connect to and push data out to a Caster over an internet connection using HTTP.  These days, most GNSS devices intended for use as reference station have the NTRIP server functionality built directly into them. Many lower cost GNSS devices do not provide this ability, but can use SNIP to connect directly with either serial or TCP/IP links.

If you have corrections from a GPS / GNSS device you need to share with others, then use SNIP.  If you need to turn a low cost device such as uBlox into an RTK Base Station, use SNIP  (and buy a good antenna).  If you need to have multiple users connected to your state run CORS account, use SNIP.  SNIP‘s free community Lite model is the most popular way on the planet to operate your own NTRIP Caster.

The data format exchanged by NTRIP is normally RTCM SC104 messages.  Rev 3.x is by far the most common for RTK uses,  while Rev 2.x is used for more primitive DGPS code correction applications needing only sub-meter accuracy.  It is also fairly common to use proprietary message formats over NTRIP as well.  NTRIP and SNIP, are more or less agnostic to the message content they relay.  However, SNIP has several integrity monitoring tools built-in for RTCM 3.x message content use.

Typically the NTRIP Clients are GNSS rover devices in the field with a thin layer of software to connect to the Caster and to feed the resulting data stream directly into the GNSS device by way of a serial port.  In more advanced GNSS devices, this software is built directly into the rover.

Need an NTRIP Caster?  We suggest you use SNIP.

Need an NTRIP Client? Here is a list of popular software.

Need to see and decode the RTCM3 messages? We suggest you use SNIP.

Need to send your corrections to a public NTRIP Caster for others?
We suggest you use RTK2go.com