ntrip

README

NTRIP Caster / Client / Server implementation in Go

Examples of NTRIP client implementations in client_test.go.

An example of setting up a Caster can be found in internal/inmemory.

Documentation

Index

• Constants
• Variables
• func NewClientRequest(url string) (*http.Request, error)
• func NewClientV1(host string, path, username, password string) (io.ReadCloser, error)
• func NewServerRequest(url string, r io.ReadCloser) (*http.Request, error)
• type Caster
  • func NewCaster(addr string, svc SourceService, logger logrus.FieldLogger) *Caster
• type CasterEntry
  • func ParseCasterEntry(casterString string) (CasterEntry, []error)
  • func (c CasterEntry) String() string
• type NetworkEntry
  • func ParseNetworkEntry(netString string) (NetworkEntry, []error)
  • func (n NetworkEntry) String() string
• type SourceService
• type Sourcetable
  • func GetSourcetable(ctx context.Context, url string) (Sourcetable, []error, error)
  • func ParseSourcetable(str string) (Sourcetable, []error)
  • func (st Sourcetable) String() string
• type StreamEntry
  • func ParseStreamEntry(streamString string) (StreamEntry, []error)
  • func (m StreamEntry) String() string

Examples

• GetSourcetable
• NewClientRequest
• NewClientRequest (Sourcetable)
• NewServerRequest

Constants

const (
	NTRIPVersionHeaderKey     string = "Ntrip-Version"
	NTRIPVersionHeaderValueV2 string = "Ntrip/2.0"
)

Variables

var (
	ErrorNotAuthorized error = fmt.Errorf("request not authorized")
	ErrorNotFound      error = fmt.Errorf("mount not found")
	ErrorConflict      error = fmt.Errorf("mount in use")
	ErrorBadRequest    error = fmt.Errorf("bad request")

	// TODO: Added this so a SourceService implementation can extract the Request ID, not sure that
	//  smuggling it in the context is the best approach
	RequestIDContextKey contextKey = contextKey("RequestID")
)

It's expected that SourceService implementations will use these errors to signal specific failures. TODO: Could use some kind of response code enum type rather than errors?

Functions

func NewClientRequest

func NewClientRequest(url string) (*http.Request, error)

NewClientRequest constructs an http.Request which can be used as an NTRIP v2 Client

Example

package main

import (
	"fmt"
	"net/http"

	"github.com/go-gnss/ntrip"
)

func main() {
	req, _ := ntrip.NewClientRequest("http://hostname:2101/mountpoint")
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		fmt.Printf("error making NTRIP request: %s", err)
	}

	if resp.StatusCode != http.StatusOK {
		fmt.Printf("received non-200 response code: %d", resp.StatusCode)
	}

	// Read from resp.Body until EOF
}

Example (Sourcetable)

package main

import (
	"fmt"
	"io/ioutil"
	"net/http"

	"github.com/go-gnss/ntrip"
)

func main() {
	req, _ := ntrip.NewClientRequest("https://ntrip.data.gnss.ga.gov.au")
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		fmt.Printf("error making NTRIP request: %s", err)
	}

	if resp.StatusCode != http.StatusOK {
		fmt.Printf("received non-200 response code: %d", resp.StatusCode)
	}

	data, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		fmt.Println("error reading from response body")
	}

	sourcetable, _ := ntrip.ParseSourcetable(string(data))
	fmt.Printf("caster has %d mountpoints available", len(sourcetable.Mounts))
}

func NewClientV1

func NewClientV1(host string, path, username, password string) (io.ReadCloser, error)

TODO: Remove v1 client

func NewServerRequest

func NewServerRequest(url string, r io.ReadCloser) (*http.Request, error)

NewServerRequest constructs an http.Request which can be used as an NTRIP v2 Server Effectively a chunked encoding POST request which is not expected to close

Example

package main

import (
	"fmt"
	"io"
	"net/http"

	"github.com/go-gnss/ntrip"
)

func main() {
	r, w := io.Pipe()

	req, _ := ntrip.NewServerRequest("http://hostname:2101/mountpoint", r)
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		fmt.Printf("error making NTRIP request: %s", err)
	}

	if resp.StatusCode != http.StatusOK {
		fmt.Printf("received non-200 response code: %d", resp.StatusCode)
	}

	w.Write([]byte("write data to the NTRIP caster"))
	w.Close()
}

Types

type Caster

type Caster struct {
	http.Server
}

Caster wraps http.Server, it provides nothing but timeouts and the Handler

func NewCaster

func NewCaster(addr string, svc SourceService, logger logrus.FieldLogger) *Caster

NewCaster constructs a Caster, setting up the Handler and timeouts - run using ListenAndServe() TODO: Consider not constructing the http.Server, and leaving Caster as a http.Handler

Then the caller can create other routes on the server, such as (for example) a /health endpoint,
or a /stats endpoint - Though those could instead be run on separate http.Server's
Also, middleware can be added to a Caster by doing `c.Handler = someMiddleware(c.Handler)`

type CasterEntry

type CasterEntry struct {
	Host                string
	Port                int
	Identifier          string
	Operator            string
	NMEA                bool
	Country             string
	Latitude            float32
	Longitude           float32
	FallbackHostAddress string
	FallbackHostPort    int
	Misc                string
}

CasterEntry for an NTRIP Sourcetable

func ParseCasterEntry

func ParseCasterEntry(casterString string) (CasterEntry, []error)

ParseCasterEntry parses a single caster from a string.

func (CasterEntry) String

func (c CasterEntry) String() string

type NetworkEntry

type NetworkEntry struct {
	Identifier string
	Operator   string
	// TODO: Authentication type - spec says: B, D, N or a comma separated list of these
	Authentication string
	Fee            bool
	NetworkInfoURL string
	StreamInfoURL  string
	// RegistrationAddress is either a URL or Email address
	RegistrationAddress string
	Misc                string
}

NetworkEntry for an NTRIP Sourcetable

func ParseNetworkEntry

func ParseNetworkEntry(netString string) (NetworkEntry, []error)

ParseNetworkEntry parses a single network entry from a string.

func (NetworkEntry) String

func (n NetworkEntry) String() string

type SourceService

type SourceService interface {
	GetSourcetable() Sourcetable
	// TODO: Specifying username and password may be limiting, could instead take the content of
	//  the auth header
	// TODO: A SourceService implementation can't support nearest base functionality because it
	//  wouldn't have access to NMEA headers - in general, it may be arbitrarily limiting to not
	//  pass the http.Request object (leaving it up to the implementation to parse headers etc.)
	Publisher(ctx context.Context, mount, username, password string) (io.WriteCloser, error)
	Subscriber(ctx context.Context, mount, username, password string) (chan []byte, error)
}

SourceService represents a provider of stream data

type Sourcetable

type Sourcetable struct {
	Casters  []CasterEntry
	Networks []NetworkEntry
	Mounts   []StreamEntry
}

Sourcetable for NTRIP Casters, returned at / as a way for users to discover available mounts

func GetSourcetable

func GetSourcetable(ctx context.Context, url string) (Sourcetable, []error, error)

GetSourcetable fetches a source table from a specific caster.

The funciton returns a list of errors which can be treated as warnings. These warnings indicate that the caster is returning an improper rtcm3 format.

Example

ctx := context.Background()
url := "http://auscors.ga.gov.au:2101"

mapping, warnings, err := GetSourcetable(ctx, url)

fmt.Println(mapping, warnings, err)

func ParseSourcetable

func ParseSourcetable(str string) (Sourcetable, []error)

ParseSourcetable parses a sourcetable from an ioreader into a ntrip style source table.

func (Sourcetable) String

func (st Sourcetable) String() string

type StreamEntry

type StreamEntry struct {
	Name          string
	Identifier    string
	Format        string
	FormatDetails string
	Carrier       string
	NavSystem     string
	Network       string
	CountryCode   string
	Latitude      float32
	Longitude     float32
	NMEA          bool
	Solution      bool
	Generator     string
	Compression   string
	// TODO: Authentication type
	Authentication string
	Fee            bool
	Bitrate        int
	Misc           string
}

StreamEntry for an NTRIP Sourcetable

func ParseStreamEntry

func ParseStreamEntry(streamString string) (StreamEntry, []error)

ParseStreamEntry parses a single mount entry.

func (StreamEntry) String

func (m StreamEntry) String() string

String representation of Mount in NTRIP Sourcetable entry format