koap
0.13.0indexedEncode and decode CoAP messages over UDP and TCP, supporting CoAP Observe. Offers header examination prior to decoding, facilitating efficient handling of CoAP message formats.
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KoAP
Kotlin CoAP encoder/decoder that provides basic support for:
Usage
Encoding
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()
Javascript Encoding Example
Encode a Message as a CoAP TCP ByteArray:
Decoding
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>()
Header
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)
Javascript Decoding Example
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)
Examples
Encoding
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) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Decoding
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
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()
)
Setup
Gradle
repositories {
mavenCentral()
}
dependencies {
implementation("com.juul.koap:koap-core:$version")
}
License
Copyright 2020 JUUL Labs, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance the License.
You may obtain a copy of the License at
http:
Unless applicable law agreed to writing, software
distributed under the License distributed an BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express implied.
See the License the specific language governing permissions
limitations under the License.