[udp] add cli-based example for UDP APIs (#2027)

src/cli/cli.cpp

@@ -201,6 +201,9 @@ const struct Command Interpreter::sCommands[] =
     { "state", &Interpreter::ProcessState },
     { "thread", &Interpreter::ProcessThread },
     { "txpowermax", &Interpreter::ProcessTxPowerMax },
+#ifndef OTDLL
+    { "udp", &Interpreter::ProcessUdp },
+#endif
     { "version", &Interpreter::ProcessVersion },
 };
 
@@ -248,6 +251,7 @@ Interpreter::Interpreter(otInstance *aInstance):
 #if OPENTHREAD_ENABLE_DNS_CLIENT
     mResolvingInProgress(0),
 #endif
+    mUdp(*this),
 #endif
     mInstance(aInstance)
 {
@@ -2487,6 +2491,15 @@ void Interpreter::ProcessVersion(int argc, char *argv[])
     OT_UNUSED_VARIABLE(argv);
 }
 
+#ifndef OTDLL
+void Interpreter::ProcessUdp(int argc, char *argv[])
+{
+    otError error;
+    error = mUdp.Process(argc, argv);
+    AppendResult(error);
+}
+#endif
+
 #if OPENTHREAD_ENABLE_COMMISSIONER && OPENTHREAD_FTD
 
 void Interpreter::ProcessCommissioner(int argc, char *argv[])