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+# CoAP Module
+The CoAP module provides a simple implementation according to [CoAP](http://tools.ietf.org/html/rfc7252) protocol.
+The basic endpoint server part is based on [microcoap](https://github.com/1248/microcoap), and many other code reference [libcoap](https://github.com/obgm/libcoap).
+
+This Module implement both Client and Server side. GET/PUT/POST/DELETE is partially supported by Client. Server can regist Lua function and varibles. No Observe or Discover supported right now.
+
+## Caution
+CoAP Module is only in the very early stage and not complete right now.
+
+## Constants
+`coap.CON`, `coap.NON` is the request type.
+
+`coap.TEXT_PLAIN`, `coap.LINKFORMAT`, `coap.XML`, `coap.OCTET_STREAM`, `coap.EXI`, `coap.JSON` is the content type.
+
+## coap.Client()
+
+Creates a CoAP client.
+
+#### Syntax
+`coap.Client()`
+
+#### Parameters
+none
+
+#### Returns
+CoAP client
+
+#### Example
+```lua
+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
+```lua
+-- 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()
+
+Issue a GET request to the server.
+
+#### Syntax
+`coap.client:get( type, uri, payload )`
+
+#### Parameters
+- `type` coap.CON, coap.NON, default 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:put()
+
+Issue a PUT request to the server.
+
+#### Syntax
+`coap.client:put( type, uri, payload )`
+
+#### Parameters
+- `type` coap.CON, coap.NON, default 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:post()
+
+Issue a POST request to the server.
+
+#### Syntax
+`coap.client:post( type, uri, payload )`
+
+#### Parameters
+- `type` coap.CON, coap.NON, default 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()
+
+Issue a DELETE request to the server.
+
+#### Syntax
+`coap.client:delete( type, uri, payload )`
+
+#### Parameters
+- `type` coap.CON, coap.NON, default 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 Server
+
+
+## coap.server:listen()
+
+Start the CoAP server on the given port.
+
+#### Syntax
+`coap.server:listen( port, ip )`
+
+#### Parameters
+- `port` server port (number).
+- `ip` optional.
+
+#### Returns
+`nil`
+
+## coap.server:close()
+
+Close the CoAP server.
+
+#### Syntax
+`coap.server:close( )`
+
+#### Parameters
+none
+
+#### Returns
+`nil`
+
+## coap.server:var()
+
+Regist a Lua variable as an endpoint in the server. the varible value then can be GET by a client via GET method, represented as an [URI](http://tools.ietf.org/html/rfc7252#section-6) to 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, default to coap.TEXT_PLAIN, see [Content Negotiation](http://tools.ietf.org/html/rfc7252#section-5.5.4)
+
+#### Returns
+`nil`
+
+#### Example
+```lua
+-- 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()
+
+Regist 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](http://tools.ietf.org/html/rfc7252#section-6) to 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 registed SHOULD be accept ONLY ONE string type parameter, and return ONE string value or return nothing.
+When the client issue 
+
+#### Syntax
+`coap.server:func( name, content_type )`
+
+#### Parameters
+- `name` the Lua function's name.
+- `content_type` optional, default to coap.TEXT_PLAIN, see [Content Negotiation](http://tools.ietf.org/html/rfc7252#section-5.5.4)
+
+#### Returns
+`nil`
+
+#### Example
+```lua
+-- 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.
+```
diff --git a/mkdocs.yml b/mkdocs.yml
index a3716780..0db30792 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -33,6 +33,7 @@ pages:
         - 'bit': 'en/modules/bit.md'
         - 'bmp085': 'en/modules/bmp085.md'
         - 'cjson': 'en/modules/cjson.md'
+        - 'coap': 'en/modules/coap.md'
         - 'crypto': 'en/modules/crypto.md'
         - 'dht': 'en/modules/dht.md'
         - 'enduser setup': 'en/modules/enduser-setup.md'