nodemcu-firmware/docs/en/modules/coap.md

CoAP Module

The CoAP module provides a simple implementation according to CoAP protocol. The basic endpoint server part is based on microcoap, and many other code reference libcoap.

This module implements both the client and the server side. GET/PUT/POST/DELETE is partially supported by the client. Server can register Lua functions and varibles. No observe or discover supported yet.

Caution

This module is only in the very early stage and not complete yet.

Constants

Constants for various functions.

coap.CON, coap.NON represent the request types.

coap.TEXT_PLAIN, coap.LINKFORMAT, coap.XML, coap.OCTET_STREAM, coap.EXI, coap.JSON represent content types.

coap.Client()

Creates a CoAP client.

Syntax

coap.Client()

Parameters

none

Returns

CoAP client

Example

cc = coap.Client()
-- assume there is a coap server at ip 192.168.100
cc:get(coap.CON, "coap://192.168.18.100:5683/.well-known/core")
-- GET is not complete, the result/payload only print out in console.
cc:post(coap.NON, "coap://192.168.18.100:5683/", "Hello")

coap.Server()

Creates a CoAP server.

Syntax

coap.Server()

Parameters

none

Returns

CoAP server

Example

-- use copper addon for firefox
cs=coap.Server()
cs:listen(5683)

myvar=1
cs:var("myvar") -- get coap://192.168.18.103:5683/v1/v/myvar will return the value of myvar: 1

all='[1,2,3]'
cs:var("all", coap.JSON) -- sets content type to json

-- function should tack one string, return one string.
function myfun(payload)
  print("myfun called")
  respond = "hello"
  return respond
end
cs:func("myfun") -- post coap://192.168.18.103:5683/v1/f/myfun will call myfun

CoAP Client

coap.client:get()

Issues a GET request to the server.

Syntax

coap.client:get(type, uri, [payload])

Parameters

• type coap.CON, coap.NON, defaults to CON. If the type is CON and request fails, the library retries four more times before giving up.
• uri the URI such as "coap://192.168.18.103:5683/v1/v/myvar", only IP addresses are supported i.e. no hostname resoltion.
• payload optional, the payload will be put in the payload section of the request.

Returns

nil

coap.client:put()

Issues a PUT request to the server.

Syntax

coap.client:put(type, uri, [payload])

Parameters

• type coap.CON, coap.NON, defaults to CON. If the type is CON and request fails, the library retries four more times before giving up.
• uri the URI such as "coap://192.168.18.103:5683/v1/v/myvar", only IP addresses are supported i.e. no hostname resoltion.
• payload optional, the payload will be put in the payload section of the request.

Returns

nil

coap.client:post()

Issues a POST request to the server.

Syntax

coap.client:post(type, uri, [payload])

Parameters

• type coap.CON, coap.NON, defaults to CON. when type is CON, and request failed, the request will retry another 4 times before giving up.
• uri the uri such as coap://192.168.18.103:5683/v1/v/myvar, only IP is supported.
• payload optional, the payload will be put in the payload section of the request.

Returns

nil

coap.client:delete()

Issues a DELETE request to the server.

Syntax

coap.client:delete(type, uri, [payload])

Parameters

• type coap.CON, coap.NON, defaults to CON. If the type is CON and request fails, the library retries four more times before giving up.
• uri the URI such as "coap://192.168.18.103:5683/v1/v/myvar", only IP addresses are supported i.e. no hostname resoltion.
• payload optional, the payload will be put in the payload section of the request.

Returns

nil

CoAP Server

coap.server:listen()

Starts the CoAP server on the given port.

Syntax

coap.server:listen(port, [ip])

Parameters

• port server port (number)
• ip optional IP address

Returns

nil

coap.server:close()

Closes the CoAP server.

Syntax

coap.server:close()

Parameters

none

Returns

nil

coap.server:var()

Registers a Lua variable as an endpoint in the server. the variable value then can be retrieved by a client via GET method, represented as an URI to the client. The endpoint path for varialble is '/v1/v/'.

Syntax

coap.server:var(name, [content_type])

Parameters

• name the Lua variable's name
• content_type optional, defaults to coap.TEXT_PLAIN, see Content Negotiation

Returns

nil

Example

-- use copper addon for firefox
cs=coap.Server()
cs:listen(5683)

myvar=1
cs:var("myvar") -- get coap://192.168.18.103:5683/v1/v/myvar will return the value of myvar: 1
-- cs:var(myvar), WRONG, this api accept the name string of the varialbe. but not the variable itself.
all='[1,2,3]'
cs:var("all", coap.JSON) -- sets content type to json

coap.server:func()

Registers a Lua function as an endpoint in the server. The function then can be called by a client via POST method. represented as an URI to the client. The endpoint path for function is '/v1/f/'.

When the client issues a POST request to this URI, the payload will be passed to the function as parameter. The function's return value will be the payload in the message to the client.

The function registered SHOULD accept ONLY ONE string type parameter, and return ONE string value or return nothing.

Syntax

coap.server:func(name, [content_type])

Parameters

• name the Lua function's name
• content_type optional, defaults to coap.TEXT_PLAIN, see Content Negotiation

Returns

nil

Example

-- use copper addon for firefox
cs=coap.Server()
cs:listen(5683)

-- function should take only one string, return one string.
function myfun(payload)
  print("myfun called")
  respond = "hello"
  return respond
end
cs:func("myfun") -- post coap://192.168.18.103:5683/v1/f/myfun will call myfun
-- cs:func(myfun), WRONG, this api accept the name string of the function. but not the function itself.