Go - IP Connection

This is the description of the Go API bindings for the IP Connection. The IP Connection manages the communication between the API bindings and the Brick Daemon or a WIFI/Ethernet Extension. Before Bricks and Bricklets can be controlled using their API an IP Connection has to be created and its TCP/IP connection has to be established.

An installation guide for the Go API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Enumerate

Download (example_enumerate.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    ipcon.RegisterEnumerateCallback(func(uid string, connectedUid string, position rune, hardwareVersion [3]uint8,
                                         firmwareVersion [3]uint8, deviceIdentifier uint16, enumerationType ipconnection.EnumerationType) {
        fmt.Printf("UID:               %s\n", uid)
        switch enumerationType {
        case ipconnection.EnumerationTypeAvailable:
            fmt.Printf("Enumeration Type:  Available\n")
        case ipconnection.EnumerationTypeConnected:
            fmt.Printf("Enumeration Type:  Connected\n")
        case ipconnection.EnumerationTypeDisconnected:
            fmt.Printf("Enumeration Type:  Disconnected\n")
            return
        }

        fmt.Printf("Connected UID:     %s\n", connectedUid)
        fmt.Printf("Position:          %c\n", position)
        fmt.Printf("Hardware Version:  %d.%d.%d\n", hardwareVersion[0], hardwareVersion[1], hardwareVersion[2])
        fmt.Printf("Firmware Version:  %d.%d.%d\n", firmwareVersion[0], firmwareVersion[1], firmwareVersion[2])
        fmt.Printf("Device Identifier: %d\n", deviceIdentifier)
        fmt.Println("")
    })

    ipcon.Enumerate()
    fmt.Println("Press enter to exit.")
    fmt.Scanln()
}

Authenticate

Download (example_authenticate.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"
const SECRET string = "My Authentication Secret!"

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()

    // Disable auto reconnect mechanism, in case we have the wrong secret. If the authentication is successful, reenable it.
    ipcon.SetAutoReconnect(false)

    ipcon.RegisterConnectCallback(func(reason ipconnection.ConnectReason) {
        if reason == ipconnection.ConnectReasonRequest {
            fmt.Println("Connected by request")
        } else if reason == ipconnection.ConnectReasonAutoReconnect {
            fmt.Println("Auto-Reconnected")
        }

        // Authenticate first...
        err := ipcon.Authenticate(SECRET)
        if err != nil {
            fmt.Println("Could not authenticate:", err)
            return
        }

        fmt.Println("Authentication succeded")
        ipcon.SetAutoReconnect(true) // ...reenable auto reconnect mechanism, as described above,
        ipcon.Enumerate()            // then trigger enumerate.
    })

    ipcon.RegisterEnumerateCallback(func(uid string, connectedUid string, position rune, hardwareVersion [3]uint8,
                                         firmwareVersion [3]uint8, deviceIdentifier uint16, enumerationType ipconnection.EnumerationType) {
        fmt.Printf("UID:               %s\n", uid)
        switch enumerationType {
        case ipconnection.EnumerationTypeAvailable:
            fmt.Printf("Enumeration Type:  Available\n")
        case ipconnection.EnumerationTypeConnected:
            fmt.Printf("Enumeration Type:  Connected\n")
        case ipconnection.EnumerationTypeDisconnected:
            fmt.Printf("Enumeration Type:  Disconnected\n")
            return
        }

        fmt.Printf("Connected UID:     %s\n", connectedUid)
        fmt.Printf("Position:          %c\n", position)
        fmt.Printf("Hardware Version:  %d.%d.%d\n", hardwareVersion[0], hardwareVersion[1], hardwareVersion[2])
        fmt.Printf("Firmware Version:  %d.%d.%d\n", firmwareVersion[0], firmwareVersion[1], firmwareVersion[2])
        fmt.Printf("Device Identifier: %d\n", deviceIdentifier)
        fmt.Println("")
    })

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()

    fmt.Println("Press enter to exit.")
    fmt.Scanln()
}

API

The IPConnection is defined in the package github.com/Tinkerforge/go-api-bindings/ipconnection.

Basic Functions

func ipconnection.New() (ipcon IPConnection)

Creates an IP Connection instance that can be used to enumerate the available devices. It is also required for the constructor of Bricks and Bricklets.

func (*IPConnection) Close()

Destroys this IP Connection and stops it's internal goroutines.

func (*IPConnection) Connect(addr string) (err error)

Creates a TCP/IP connection to the given addr with the form "host:port", as described here . The host and port can refer to a Brick Daemon or to a WIFI/Ethernet Extension.

Devices can only be controlled when the connection was established successfully.

func (*IPConnection) Disconnect()

Disconnects the TCP/IP connection from the Brick Daemon or the WIFI/Ethernet Extension.

func (*IPConnection) Authenticate(secret string) (err error)

Performs an authentication handshake with the connected Brick Daemon or WIFI/Ethernet Extension. If the handshake succeeds the connection switches from non-authenticated to authenticated state and communication can continue as normal. If the handshake fails then the connection gets closed. Authentication can fail if the wrong secret was used or if authentication is not enabled at all on the Brick Daemon or the WIFI/Ethernet Extension.

See the authentication tutorial for more information.

func (*IPConnection) GetConnectionState() (state ConnectionState)

Can return the following states:

  • ipconnection.ConnectionStateDisconnected = 0: No connection is established.
  • ipconnection.ConnectionStateConnected = 1: A connection to the Brick Daemon or the WIFI/Ethernet Extension is established.
  • ipconnection.ConnectionStatePending = 2: IP Connection is currently trying to connect.
func (*IPConnection) SetAutoReconnect(autoReconnectEnabled bool)

Enables or disables auto-reconnect. If auto-reconnect is enabled, the IP Connection will try to reconnect to the previously given address, if the currently existing connection is lost. Therefore, auto-reconnect only does something after a successful Connect() call.

Default value is true.

func (*IPConnection) GetAutoReconnect() (autoReconnect bool)

Returns true if auto-reconnect is enabled, false otherwise.

func (*IPConnection) SetTimeout(timeout time.Duration)

Sets the timeout for getters and for setters for which the response expected flag is activated.

Default timeout is 2500 ms.

func (*IPConnection) GetTimeout() (timeout time.Duration)

Returns the timeout as set by SetTimeout().

func (*IPConnection) Enumerate()

Broadcasts an enumerate request. All devices will respond with an enumerate callback.

Callbacks

Callbacks can be registered to be notified about events. The registration is done with Register*Callback() functions of the IPConnection object. For example:

registrationId := ipcon.RegisterExampleCallback(func(param type) {
    fmt.Println(param)
});

The available events are described below. It is possible to add several callbacks and to remove them with the corresponding Deregister*Callback() function, which expects a registration ID returned by Register*Callback().

func (*IPConnection) RegisterEnumerateCallback(func(uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, enumerationType EnumerationType)) (registrationId uint64)

The callback receives seven parameters:

  • uid: The UID of the device.
  • connectedUid: UID where the device is connected to. For a Bricklet this will be a UID of the Brick where it is connected to. For a Brick it will be the UID of the bottom Master Brick in the stack. For the bottom Master Brick in a stack this will be "0". With this information it is possible to reconstruct the complete network topology.
  • position: For Bricks: '0' - '8' (position in stack). For Bricklets: 'a' - 'h' (position on Brick) or 'i' (position of the Raspberry Pi (Zero) HAT) or 'z' (Bricklet on Isolator Bricklet).
  • hardwareVersion: Major, minor and release number for hardware version.
  • firmwareVersion: Major, minor and release number for firmware version.
  • deviceIdentifier: A number that represents the device.
  • enumerationType: Type of enumeration.

Possible enumeration types are:

  • ipconnection.EnumerationTypeAvailable = 0: Device is available (enumeration triggered by user: Enumerate()). This enumeration type can occur multiple times for the same device.
  • ipconnection.EnumerationTypeConnected = 1: Device is newly connected (automatically send by Brick after establishing a communication connection). This indicates that the device has potentially lost its previous configuration and needs to be reconfigured.
  • ipconnection.EnumerationTypeDisconnected = 2: Device is disconnected (only possible for USB connection). In this case only UID and EnumerationType are valid.

It should be possible to implement plug-and-play functionality with this (as is done in Brick Viewer).

The device identifier numbers can be found here. There are also constants for these numbers named following this pattern:

<device-package>.DeviceIdentifier

For example: master_brick.DeviceIdentifier or ambient_light_bricklet.DeviceIdentifier.

func (*IPConnection) RegisterConnectCallback(func(reason ConnectReason)) (registrationId uint64)

This event is triggered whenever the IP Connection got connected to a Brick Daemon or to a WIFI/Ethernet Extension, possible reasons are:

  • ipconnection.ConnectReasonRequest = 0: Connection established after request from user.
  • ipconnection.ConnectReasonAutoReconnect = 1: Connection after auto-reconnect.
func (*IPConnection) RegisterDisconnectCallback(func(reason DisconnectReason)) (registrationId uint64)

This event is triggered whenever the IP Connection got disconnected from a Brick Daemon or to a WIFI/Ethernet Extension, possible reasons are:

  • ipconnection.DisconnectReasonRequest = 0: Disconnect was requested by user.
  • ipconnection.DisconnectReasonError = 1: Disconnect because of an unresolvable error.
  • ipconnection.DisconnectReasonShutdown = 2: Disconnect initiated by Brick Daemon or WIFI/Ethernet Extension.