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                NTRIP Client for POSIX systems
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Easy example NTRIP client for POSIX systems.
Copyright (C) 2003-2007 by Dirk Stoecker <soft@dstoecker.de>
    
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
or read http://www.gnu.org/licenses/gpl.txt

Files in ntripclient.zip
-----------------------------
ntripclient.c:    Ntrip POSIX client source code
serial.c:         source code to support for serial output
README:           Dokumentation
startntripclient: Shell script to start client
makefile:         Easy makefile to build source

Ntrip
-----
The ntripclient is an HTTP client based on 'Networked Transport
of RTCM via Internet Protocol' (Ntrip). This is an application-level 
protocol streaming Global Navigation Satellite System (GNSS) data over 
the Internet. Ntrip Version 1.0 is a generic, stateless protocol based 
on the Hypertext Transfer Protocol HTTP/1.1. The HTTP objects are 
enhanced to GNSS data streams.

The primary motivation for Ntrip Version 2.0 is to develop a fully 
HTTP-compatible Internet protocol standard that would work with proxy 
servers and to add an optional data transport via UDP. Hence, one 
Ntrip Version 2.0 transport approach is still based on HTTP1.1 on top 
of TCP. The second Ntrip Version 2.0 transport approach is based on 
both, the Internet Standard Protocol RTSP (Real Time Streaming Protocol) 
for stream control on top of TCP and the Internet Standard Protocol RTP 
(Real Time Transport Protocol) for data transport on top of 
connectionless UDP.

Ntrip is designed for disseminating differential correction data 
(e.g in the RTCM-104 format) or other kinds of GNSS streaming data to
stationary or mobile users over the Internet, allowing simultaneous PC,
Laptop, PDA, or receiver connections to a broadcasting host. Ntrip 
supports Wireless Internet access through Mobile IP Networks like GSM, 
GPRS, EDGE, or UMTS.

Ntrip is implemented in three system software components: NtripClients, 
NtripServers and NtripCasters. The NtripCaster is the actual HTTP 
server program whereas NtripClient and NtripServer are acting as HTTP 
clients.

ntripclient
-----------
This POSIX Ntrip client program is written under GNU General Public 
License in C programming language. The program reads data from an Ntrip 
Broadcaster and writes on standard output for further redirection 
of data to a file or COM-port. PLEASE NOTE THAT THIS PROGRAM VERSION
DOES NOT HANDLE POTENTIALLY OCCURRING INTERRUPTIONS OF COMMUNICATION
OR NETWORK CONGESTION SITUATIONS. Its distribution may stimulate
those intending to write their own client program.

Call the program with following arguments:

./ntripclient -s server -u user ...
 -m --mountpoint the requested data set or sourcetable filtering criteria
 -s --server     the server name or address
 -p --password   the login password
 -r --port       the server port number (default 2101)
 -u --user       the user name
 -M --mode       mode for data request
     Valid modes are:
     1, h, http     NTRIP Version 2.0 Caster in TCP/IP mode
     2, r, rtsp     NTRIP Version 2.0 Caster in RTSP/RTP mode
     3, n, ntrip1   NTRIP Version 1.0 Caster
     4, a, auto     automatic detection (default)
     5, u, udp      NTRIP Version 2.0 Caster in UDP mode
or using an URL:
./ntripclient ntrip:mountpoint[/user[:password]][@[server][:port][@proxyhost[:proxyport]]][;nmea]

Expert options:
 -n --nmea       NMEA string for sending to server
 -b --bitrate    output bitrate
 -I --initudp    send initial UDP packet for firewall handling
 -P --udpport    set the local UDP port
 -S --proxyhost  proxy name or address
 -R --proxyport  proxy port, optional (default 2101)

Serial input/output:
 -D --serdevice  serial device for output
 -B --baud       baudrate for serial device
 -T --stopbits   stopbits for serial device
 -C --protocol   protocol for serial device
 -Y --parity     parity for serial device
 -A --databits   databits for serial device
 -l --serlogfile logfile for serial data

The argument '-h' will cause a HELP on the screen.
Without any argument ntripclient will provide the a table of
available resources (sourcetable).

Sourcetable filtering
----------------------
A missing argument '-m' leads to the output of the complete broadcaster
sourcetable. This may comprise hundreds of lines in case of large 
networks. To limit the output, the sourcetable contents can be filtered 
through entering the argument '-m' followed by a sequence of query strings,
one for each sourcetable data field. Only those sourcetable lines are
returned from the broadcaster whoes data fields match the corresponding
query strings. A sequence of query strings has to be initiated by a '?'
and a semicolon is acting as query string delimiter in analogy to the
sourcetable data field delimiter.

Note that for fully understanding the sourcetable filtering option
you have to make yourself familiar with the details of the sourcetable
contents. In general, search criterias can be applied on each sourcetable 
data field.

The following query string operators are available for integer and
floating-point numbers in the sourcetable lines:

- Equation operators: <, >, >=, <=, =, != (not equal)
- Approximation operator: ~n (find value with minimal distance to n)

The following query string operators are available for alphanumeric
strings in the sourcetable lines:

- Wildcard operator: '*' means any number of characters
- Alternation operator: expression|expression
- Grouping operator: (expression)
- Any character matching for strings (case insensitivity)

The following operators are available for both text as well as integer
and floating-point numbers in the sourcetable lines:

- Logical operators: ! (NOT), & (AND), | (OR)
- Grouping operator: [!] (Expression)

Examples:

- Searching in a sourcetable for streams in Germany would require
  entering the '-m' argument followed by
  the query string:
  ?STR;;;;;;DEU

- Searching in a sourcetable for free streams fom the EUREF network and
  coming from the Frankfurt area would require entering the '-m' argument
  followed by the query string:
  ?STR;;;;;;;EUREF;;=>50&<=51;=>8.1&<8.6;;;;;N

Compilation/Installation
------------------------
Please extract the archive and copy its contents into an appropriate
directory. Compile the source code under POSIX systems by calling 'make'.

To compile the source code on a Windows system where a mingw gcc
compiler is available, you may like to run the following command:

gcc -DWINDOWSVERSION -o ntripclient.exe ntripclient.c -lwsock32

Registration
------------
Some of the data streams (mountpoints) from an NtripCaster may be
available for test, demonstration, and evaluation purposes and
accessible without authentication/authorization. For accessing other
data streams (mountpoints) the user needs a user-ID and a
user password. Authorization can be provided for a single stream,
for a group of streams (network) or for all available streams.
Currently, registration can be requested via the registration form
on http://igs.bkg.bund.de/index_ntrip_reg.htm

Ntrip Broadaster Address and Port
---------------------------------
The current Internet address of the Ntrip Broadcaster is
www.euref-ip.net. The port number is 2101.

Disclaimer
----------
Note that this ntripclient program is for experimental use
only. The BKG disclaims any liability nor responsibility to any 
person or entity with respect to any loss or damage caused, or alleged 
to be caused, directly or indirectly by the use and application of the 
Ntrip technology.

Further Information
-------------------
http://igs.bkg.bund.de/index_ntrip.htm
euref-ip@bkg.bund.de