[coap] add CoAP(s) block-wise transfer support to CoAP(s) client and server (#4247)

Implemented CoAP/-s block-wise transfer according to RFC 7959. The
implementation includes methods and functions available to the
application layer to add Block1 and Block2 option values to a coap
message and an automatic block-wise transfer enabled by the compile
switch "COAP_BLOCK".

tests/scripts/thread-cert/node.py

@@ -1884,6 +1884,12 @@ class NodeImpl:
         """
         return self._coap_rq('get', ipaddr, uri, con, payload)
 
+    def coap_get_block(self, ipaddr, uri, size=16, count=0):
+        """
+        Send a GET request via CoAP.
+        """
+        return self._coap_rq_block('get', ipaddr, uri, size, count)
+
     def coap_observe(self, ipaddr, uri, con=False, payload=None):
         """
         Send a GET request via CoAP with Observe set.
@@ -1896,12 +1902,24 @@ class NodeImpl:
         """
         return self._coap_rq('post', ipaddr, uri, con, payload)
 
+    def coap_post_block(self, ipaddr, uri, size=16, count=0):
+        """
+        Send a POST request via CoAP.
+        """
+        return self._coap_rq_block('post', ipaddr, uri, size, count)
+
     def coap_put(self, ipaddr, uri, con=False, payload=None):
         """
         Send a PUT request via CoAP.
         """
         return self._coap_rq('put', ipaddr, uri, con, payload)
 
+    def coap_put_block(self, ipaddr, uri, size=16, count=0):
+        """
+        Send a PUT request via CoAP.
+        """
+        return self._coap_rq_block('put', ipaddr, uri, size, count)
+
     def _coap_rq(self, method, ipaddr, uri, con=False, payload=None):
         """
         Issue a GET/POST/PUT/DELETE/GET OBSERVE request.
@@ -1918,6 +1936,20 @@ class NodeImpl:
         self.send_command(cmd)
         return self.coap_wait_response()
 
+    def _coap_rq_block(self, method, ipaddr, uri, size=16, count=0):
+        """
+        Issue a GET/POST/PUT/DELETE/GET OBSERVE BLOCK request.
+        """
+        cmd = 'coap %s %s %s' % (method, ipaddr, uri)
+
+        cmd += ' block-%d' % size
+
+        if count is not 0:
+            cmd += ' %d' % count
+
+        self.send_command(cmd)
+        return self.coap_wait_response()
+
     def coap_wait_response(self):
         """
         Wait for a CoAP response, and return it.
@@ -1938,7 +1970,10 @@ class NodeImpl:
             observe = int(observe, base=10)
 
         if payload is not None:
-            payload = binascii.a2b_hex(payload).decode('UTF-8')
+            try:
+                payload = binascii.a2b_hex(payload).decode('UTF-8')
+            except UnicodeDecodeError:
+                pass
 
         # Return the values received
         return dict(source=source, observe=observe, payload=payload)
@@ -2004,6 +2039,14 @@ class NodeImpl:
         self.send_command(cmd)
         self._expect_done()
 
+    def coap_set_resource_path_block(self, path, count=0):
+        """
+        Set the path for the CoAP resource and how many blocks can be received from this resource.
+        """
+        cmd = 'coap resource %s %d' % (path, count)
+        self.send_command(cmd)
+        self._expect('Done')
+
     def coap_set_content(self, content):
         """
         Set the content of the CoAP resource.