Test Connectivity to a Secure CoAP Resource Using the OT CLI

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OpenThread offers both Secure CoAP server and client functionality, enabling devices to connect to resources on the Secure CoAP server and to observe each resource for a change in its current state.

Secure CoAP uses Datagram Transport Layer Security (DTLS) to establish secure, end-to-end connections.

The Secure CoAP agent provided in the CLI can act as either the Secure CoAP client or Secure CoAP server.

This guide provides basic tasks that use some of the more common Secure CoAP (coaps) commands.

Secure CoAP commands

For a list of Secure CoAP commands, type help:

coaps help
connect
delete
disconnect
get
isclosed
isconnactive
isconnected
post
psk
put
resource
set
start
stop
x509
Done

CLI Command Reference

For descriptions and syntax of all commands, refer to the CLI Command Reference. The Secure CoAP commands begin alphabetically with coaps connect.

Example of Secure CoAP server and client command usage

This example uses basic CLI commands to start a Secure CoAP server and client, create a test resource on the Secure CoAP server, and have the Secure CoAP client interact with the resource. Sample data are used for illustrative purposes.

Configure DTLS ciphersuites

The coaps CLI provides psk and x509 commands that can be used with the PSK key and X.509 Certificate. For command syntax and examples, refer to coaps psk and coaps x509.

Set up the Secure CoAP server

On the Secure CoAP server node, perform the following steps:

Start the Secure CoAP agent.
```
coaps start
Done
```
Create a test resource.
```
coaps resource test-resource
Done
```

Set up the Secure CoAP client

On the Secure CoAP client node, perform the following steps:

Start the Secure CoAP agent:
```
coaps start
Done
```

Run the connect command to initialize a DTLS session with a peer:

coaps connect fdde:ad00:beef:0:9903:14b:27e0:5744
Done
coaps connected

Run the get command to obtain information about the resource:
```
coaps get test-resource
Done
coaps response from fdde:ad00:beef:0:9903:14b:27e0:5744 with payload: 68656c6c6f576f726c6400
```
The last portion of the server response is the term with payload:, followed by all payload bytes in hexadecimal digit format. In the example, with payload: 68656c6c6f576f726c6400 indicates that the current payload for the resource is the hexadecimal value 68656c6c6f576f726c6400, which converts to the string helloWorld. For more information about using the payload option, refer to coaps post.
You can modify the resource using the put command:
```
coaps put test-resource con hellothere
Done
coaps response from fdde:ad00:beef:0:9903:14b:27e0:5744
```
In this example, con means that you want a reliable message, which is obtained using a confirmable message (con), to be sent to the Secure CoAP server. The default is to send a non-confirmable (non-con) message.

The string hellothere is an example of using the optional payload parameter when the type is either con or non-con. For more information, refer to coaps put.

The server responds with its IPv6 address to indicate the request was handled.

Responses sent to the Secure CoAP server

On the server, output from this example would be similar to the following:

coaps request from fdde:ad00:beef:0:9e68:576f:714c:f395 GET
coaps response sent
coaps request from fdde:ad00:beef:0:9e68:576f:714c:f395 PUT with payload: 68656c6c6f7468657265
coaps response sent

The payload value of 68656c6c6f7468657265 is the string hellothere converted to ASCII code byte sequence.