Websocket connection undefined (#252)

Fix _updateSubscriptions to safely access connections and add tests

lib/httpServer.js

@@ -1,4 +1,5 @@
-var http = require("http");
+const http = require("http");
+const { rpcError } = require("./utils/to");
 
 module.exports = function(provider, logger) {
   var server = http.createServer(function(request, response) {
@@ -50,6 +51,14 @@ module.exports = function(provider, logger) {
               logger.log(payload.method);
             }
 
+            // http connections do not support subscriptions
+            if (payload.method === "eth_subscribe" || payload.method === "eth_unsubscribe") {
+              headers["Content-Type"] = "application/json";
+              response.writeHead(400, headers);
+              response.end(rpcError(payload.id, -32000, "notifications not supported"));
+              break;
+            }
+
             provider.send(payload, function(_, result) {
               headers["Content-Type"] = "application/json";
               response.writeHead(200, headers);

lib/utils/to.js

@@ -110,5 +110,16 @@ module.exports = {
     }
     var bufVal = utils.toBuffer(val);
     return utils.bufferToInt(bufVal);
+  },
+
+  rpcError: function(id, code, msg) {
+    return JSON.stringify({
+      jsonrpc: "2.0",
+      id: id,
+      error: {
+        code: code,
+        message: msg
+      }
+    });
   }
 };

lib/webSocketServer.js

@@ -127,5 +127,9 @@ ConnectionManager.prototype._logPayload = function(payload) {
 };
 
 ConnectionManager.prototype._updateSubscriptions = function(notification) {
-  this.connectionsBySubscriptionId[notification.params.subscription].connection.send(JSON.stringify(notification));
+  const subscription = this.connectionsBySubscriptionId[notification.params.subscription];
+  // Safety check for subscription/connection.
+  if (subscription) {
+    subscription.connection.send(JSON.stringify(notification));
+  }
 };