NPL message refactor. (#132)

* Implemented feeding and broadcasting npl messages from the contract execution in real-time.
* Replaced npl pipe with domain sockets.
* Refactored npl read and write in nodejs echo contract

examples/nodejs_contract/echo_contract.js

@@ -9,19 +9,44 @@ const hpc = new HotPocketContract();
 if (!hpc.readonly)
     fs.appendFileSync("exects.txt", "ts:" + hpc.timestamp + "\n");
 
-Object.keys(hpc.users).forEach(function (key) {
+Object.keys(hpc.users).forEach(async (key) => {
 
     const user = hpc.users[key];
-    user.readInput().then(inputBuf => {
-        if (inputBuf) {
-            const userInput = inputBuf.toString("utf8");
-
-            if (userInput == "ts")
-                user.sendOutput(fs.readFileSync("exects.txt"));
-            else
-                user.sendOutput("Echoing: " + userInput);
-        }
-    })
+    const inputBuf = await user.readInput();
+    if (inputBuf) {
+        const userInput = inputBuf.toString("utf8");
+        if (userInput == "ts")
+            user.sendOutput(fs.readFileSync("exects.txt"));
+        else
+            user.sendOutput("Echoing: " + userInput);
+    }
 });
 
+const npl = hpc.npl;
+
+// Npl channel always connected if contract is not in readonly mode.
+// Smart contract developer has to mannually close the channel once the execution logic is complete.
+if (npl) {
+    npl.closeNplChannel();
+}
+
+// Npl message sending and receiving template.
+// if (npl) {
+//     let i = 0;
+//     let interval = setInterval(() => {
+//         npl.sendOutput(`npl${i} from contract`);
+//         if (i == 5) {
+//             clearInterval(interval);
+//             npl.closeNplChannel();
+//         }
+//         i++;
+//     }, 500);
+
+//     npl.events.on("message", msg => {
+//         if (msg) {
+//             console.log(msg);
+//         }
+//     });
+// }
+
 //console.log("===Echo contract ended===");