Finalize first version of README file adding example for the server o…

…peration, Future work and contribution statements

README.md

@@ -5,7 +5,7 @@ It is a port of an Arduino C++ library [CoAP-simple-library](https://github.com/
 
 Its main difference compared to the established Python implementations [aiocoap](https://github.com/chrysn/aiocoap) and [CoAPthon](https://github.com/Tanganelli/CoAPthon) is its size and complexity since this library will be used on microcontrollers that support MicroPython such as: Pycom devices, ESP32, ESP8266.
 
-The first goal of this implementation is to provide basic functionality to send and receive data. DTLS and/or any special features of CoAP as defined in the RFC's, will be examined and implented in the future.
+The first goal of this implementation is to provide basic functionality to send and receive data. DTLS and/or any special features of CoAP as defined in the RFC's, will be examined and implemented in the future.
 
 # Supported operations
 
@@ -14,9 +14,9 @@ The first goal of this implementation is to provide basic functionality to send
 * POST
 * GET
 
-## Example of usage
+### Example of usage
+Here is an example using the CoAP client functionality to send requests and receive responses. (this example is part of [examples/pycom_wifi_coap_client.py](https://github.com/insighiot/microCoAPy/blob/master/examples/pycom_wifi_coap_client.py))
 
-Here is an example using the CoAP client functionality to send requests and receive responses.
 
 ```python
 import microcoapy.microcoapy as microcoapy
@@ -40,6 +40,7 @@ client.poll(2000)
 client.stop()
 ```
 
+#### Code explained
 Lets examine the above code and explain its purpose.
 
 ```python
@@ -56,23 +57,112 @@ During this step, the CoAP object get initialized. A callback handler is also cr
 client.start()
 ```
 
-The call to the _start_ function is where the UDP socket gets created. By default it gets bind to the defalut CoAP port 5683. If a custom port is needed, pass it as argument to the _start_ function.
+The call to the _start_ function is where the UDP socket gets created. By default it gets bind to the default CoAP port 5683. If a custom port is required, pass it as argument to the _start_ function.
 
 ```python
 bytesTransferred = client.get(_SERVER_IP, _SERVER_PORT, "current/measure")
 print("[GET] Sent bytes: ", bytesTransferred)
 ```
 
-Having the socket ready, it is time to send our request. In this case we send a simple GET request to the specific address (ex. 192.168.1.2:5683). The _get_ function returns the number of bytes that has been able to send. So in case of error, 0 will be returned.  
+Having the socket ready, it is time to send our request. In this case we send a simple GET request to the specific address (ex. 192.168.1.2:5683). The _get_ function returns the number of bytes that have been sent. So in case of error, 0 will be returned.  
 
 ```python
 client.poll(2000)
 ```
 
 Since a GET request has been posted, most likely it would be nice to receive and process the server response. For this reason we call _poll_ function that will try to read incoming messages for 2000 milliseconds. Upon timeout the execution will continue to the next command.
 
-If a packet gets received during that period of type that is an _ACK_ to our request or a report (ex. _404_), the callback that has been registered at the  beginning will be called. 
+If a packet gets received during that period of type that is an _ACK_ to our request or a report (ex. _404_), the callback that has been registered at the beginning will be called.
 
+```python
+client.stop()
+```
+
+Finally, stop is called to gracefully close the socket. It is preferable to have a corresponding call of _stop_ to each call of _start_ function because in special cases such as when using mobile modems, the modem might stuck when running out of available sockets.  
+
+To send POST or PUT message replace the call of _get_ function with:
+```python
+bytesTransferred = client.put(_SERVER_IP, _SERVER_PORT, "led/turnOn", "test",
+                                 None, microcoapy.COAP_CONTENT_TYPE.COAP_TEXT_PLAIN)
+```
+or
+```python
+bytesTransferred = client.post(_SERVER_IP, _SERVER_PORT, "led/turnOn", "test",
+                                 None, microcoapy.COAP_CONTENT_TYPE.COAP_TEXT_PLAIN)
+```
+
+For details on the arguments please advice the __documentation__ (link to be soon provided).
 
 ## CoAP server
-* Starts a server and calls custom callbacks upon receiving an incoming request. The respose needs to be defined by the user of the library.
+Starts a server and calls custom callbacks upon receiving an incoming request. The response needs to be defined by the user of the library.
+
+### Example of usage
+
+Here is an example using the CoAP server functionality to receive requests and respond back. (this example is part of [examples/pycom_wifi_coap_server.py](https://github.com/insighiot/microCoAPy/blob/master/examples/pycom_wifi_coap_server.py))
+
+```python
+import microcoapy.microcoapy as microcoapy
+# your code to connect to the network
+#...
+client = microcoapy.Coap()
+
+def measureCurrent(packet, senderIp, senderPort):
+    print('Measure-current request received:', packet, ', from: ', senderIp, ":", senderPort)
+    client.sendResponse(senderIp, senderPort, packet.messageid,
+                      None, microcoapy.COAP_RESPONSE_CODE.COAP_CONTENT,
+                      microcoapy.COAP_CONTENT_TYPE.COAP_NONE, "222")
+
+client.addIncomingRequestCallback('current/measure', measureCurrent)
+
+client.start()
+
+# wait for incoming request for 60 seconds
+timeoutMs = 60000
+start_time = time.ticks_ms()
+while time.ticks_diff(time.ticks_ms(), start_time) < timeoutMs:
+    client.poll(60000)
+
+client.stop()
+```
+
+#### Code explained
+Lets examine the above code and explain its purpose. For details on _start_ and _stop_ functions advice the previous paragraph of the client example.
+
+```python
+def measureCurrent(packet, senderIp, senderPort):
+    print('Measure-current request received:', packet, ', from: ', senderIp, ":", senderPort)
+    client.sendResponse(senderIp, senderPort, packet.messageid,
+                      None, microcoapy.COAP_RESPONSE_CODE.COAP_CONTENT,
+                      microcoapy.COAP_CONTENT_TYPE.COAP_NONE, "222")
+
+client.addIncomingRequestCallback('current/measure', measureCurrent)
+```
+
+This is the main step to prepare the CoAP instance to behave as a server: receive and handle requests. First we create a function _measureCurrent_ that takes as arguments the incoming packet, the sender IP and Port. This function will  be used as a callback and will be triggered every time a specific URI path is provided in the incoming request.
+
+This URL is defined upon registering the callback to the CoAP instance by calling _addIncomingRequestCallback_ function. After this call, if a CoAP GET/PUT/POST packet is received with URI path: coap://<IP>/current/measure , the callback will be triggered.
+
+By default, the server does not send any response. This is a responsibility of the user to send (if needed) the appropriate response.
+
+In this example, we reply with a response message packet (which has the same message id as the incoming request packet) whose payload is the actual value of the reading that has just been executed (in the example it is a hard-coded value of 222).
+
+```python
+timeoutMs = 60000
+start_time = time.ticks_ms()
+while time.ticks_diff(time.ticks_ms(), start_time) < timeoutMs:
+    client.poll(60000)
+```
+
+Finally, since the functions _loop_ and _poll_ __can handle a since packet per run__, we wrap its call to a while loop and wait for incoming messages.
+
+# Future work
+
+* Since this library is quite fresh, the next period will be full of testing.
+* write documentation on GitHub
+* write documentation as docstring in the code at the declaration of each function
+* create more examples with new scenarios and more platforms (ex. ESP32, ESP8266, etc.)
+* enhancments on funtionality as needed
+
+# Issues & contributions
+
+It would be our pleasure to receive comments, bug reports and/or contributions. To do this use the Issues and Pull requests of GitHub.