Kotlin CoAP encoder/decoder that provides basic support for:
ByteArrays of encoded CoAP messages can be created from Message objects (either Message.Udp or
Message.Tcp depending on the desired encoding).
To encode a Message as a CoAP UDP ByteArray:
import com.juul.koap.Message.Udp
import com.juul.koap.encode
val message = Message.Udp(/* ... */)
val encoded = message.encode()Similarly, to encode a Message as a CoAP TCP ByteArray:
import com.juul.koap.Message.Tcp
import com.juul.koap.encode
val message = Message.Tcp(/* ... */)
val encoded = message.encode()Encode a Message as a CoAP TCP ByteArray:
import kotlin from 'kotlin'
import koapModule from '@juullabs/koap'
const koap = koapModule.com.juul.koap
let method = koap.Message.Code.Method.GET
let token = new kotlin.Long(66)
let emptyPayload = new Uint8Array()
let optionsArray = [
new koap.Message.Option.UriPath('info'),
new koap.Message.Option.UriQuery('batt')
]
let optionsList = new kotlin.kotlin.collections.ArrayList(optionsArray)
let message = new koap.Message.Tcp(
method,
token,
optionsList,
emptyPayload
)
let encoded = koap.encode(message)Encoded CoAP messages (in the form of ByteArrays) can be decoded to Message objects (either
Message.Udp or Message.Tcp, depending on the encoding).
To decode a ByteArray containing a message encoded as CoAP UDP:
import com.juul.koap.Message.Udp
import com.juul.koap.decode
val encoded: ByteArray // Encoded message that adheres to RFC 7252.
val message = encoded.decode<Udp>()Similarly, to decode a ByteArray encoded as a CoAP TCP message:
import com.juul.koap.Message.Tcp
import com.juul.koap.decode
val encoded: ByteArray // Encoded message that adheres to RFC 8323.
val message = encoded.decode<Tcp>()If it's desirable to examine the header prior to decoding the entire encoded CoAP message, then
ByteArray.decodeUdpHeader or ByteArray.decodeTcpHeader extension functions are available. The
remaining encoded CoAP message can then be decoded by passing the header to the ByteArray.decode
extension function, for example:
val encoded: ByteArray // Encoded message that adheres to RFC 7252.
val header = encoded.decodeUdpHeader()
// Examine header and determine that message should be decoded:
val message = encoded.decode(header)Decode a ByteArray as a CoAP TCP Message:
import kotlin from 'kotlin'
import koapModule from '@juullabs/koap'
const koap = koapModule.com.juul.koap
let encoded = new Uint8Array(/* ...message data... */)
let message = koap.decodeTcp(encoded)val message = Message.Udp(
type = Confirmable,
code = GET,
id = 0xFEED,
token = 0xCAFE,
options = listOf(
UriPath("example")
),
payload = byteArrayOf()
)Encoding the above Message will produce the following encoded data:
42 01 FE ED CA FE B7 65 78 61 6D 70 6C 65
Encoded messages adhere to the format described in Figure 7: Message Format of RFC 7252:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver| T | TKL | Code | Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token (if any, TKL bytes) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 1 1 1 1 1 1| Payload (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field(s) | Hex | Description |
|---|---|---|
| Ver, T, TKL | 42 |
4 = Version: 1, Type: 0 (Confirmable)2 = Token Length: 2 |
| Code | 01 |
Code: 0.01 (GET) |
| Message ID | FE ED |
|
| Token | CA FE |
|
| Option delta/length | B7 |
B = Delta option: 11 (Uri-Path)7 = Delta length: 7 |
| Option value | 65 78 61 6D 70 6C 65 |
"example" |
Assuming an encoded message consists of the following CoAP UDP encoded data:
42 01 FE ED CA FE B5 2F 74 65 73 74 FF 48 65 6C 6C 6F 20 55 44 50 21
| Field(s) | Hex | Description |
|---|---|---|
| Ver, T, TKL | 42 |
4 = Version: 1, Type: 0 (Confirmable)2 = Token Length: 2 |
| Code | 01 |
Code: 0.01 (GET) |
| Message ID | FE ED |
|
| Token | CA FE |
|
| Option delta/length | B5 |
B = Delta option: 11 (Uri-Path)5 = Delta length: 5 |
| Option value | 2F 74 65 73 74 |
"/test" |
| Payload marker | FF |
Signifies the end of Options and beginning of payload. |
| Payload | 48 65 6C 6C 6F 20 55 44 50 21 |
"Hello UDP!" |
The above encoded UDP message can be decoded to a Message.Udp via ByteArray.decode extension
function:
val message = encoded.decode<Udp>()The resulting Message will be equivalent to:
Message.Udp(
type = Confirmable,
code = GET,
id = 0xFEED,
token = 0xCAFE,
options = listOf(
UriPath("/test")
),
payload = "Hello UDP!".toByteArray()
)
repositories {
mavenCentral()
}
dependencies {
implementation("com.juul.koap:koap-core:$version")
}Copyright 2020 JUUL Labs, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
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