diff --git a/bin/bootstrap.js b/bin/bootstrap.js
index 6a8a402..23cb070 100644
--- a/bin/bootstrap.js
+++ b/bin/bootstrap.js
@@ -17,7 +17,7 @@ function obtainConfig(file) {
   return json;
 }
 
-module.exports = function bootstrap(configPath, {core: {Hub, Config}}) {
+module.exports = function bootstrap(configPath, {Hub, Config}) {
   try {
     Config.init(obtainConfig(configPath));
     if (cluster.isMaster && __WORKERS__ > 0) {
diff --git a/src/core/config.js b/src/core/config.js
index 8f24d92..3b4d932 100644
--- a/src/core/config.js
+++ b/src/core/config.js
@@ -10,11 +10,6 @@ import {getPresetClassByName} from '../presets';
 import {isValidHostname, isValidPort, logger} from '../utils';
 import {DNS_DEFAULT_EXPIRE} from './dns-cache';
 
-export const AVAILABLE_PROTOCOLS = [
-  'tcp', 'socks', 'socks5', 'socks4', 'socks4a',
-  'http', 'https', 'ws', 'tls'
-];
-
 function loadFileSync(file) {
   return fs.readFileSync(path.resolve(process.cwd(), file));
 }
@@ -336,9 +331,13 @@ export class Config {
     if (typeof protocol !== 'string') {
       throw Error('service protocol is invalid');
     }
+    const AVAILABLE_LOCAL_PROTOCOLS = [
+      'tcp', 'socks', 'socks5', 'socks4', 'socks4a',
+      'http', 'https', 'ws', 'tls'
+    ];
     const _protocol = protocol.slice(0, -1);
-    if (!AVAILABLE_PROTOCOLS.includes(_protocol)) {
-      throw Error(`service protocol must be: ${AVAILABLE_PROTOCOLS.join(', ')}`);
+    if (!AVAILABLE_LOCAL_PROTOCOLS.includes(_protocol)) {
+      throw Error(`service protocol must be: ${AVAILABLE_LOCAL_PROTOCOLS.join(', ')}`);
     }
     if (_protocol === 'tls') {
       if (typeof json.tls_cert !== 'string' || json.tls_cert === '') {
diff --git a/src/core/hub.js b/src/core/hub.js
index e00b9bc..7fd399d 100644
--- a/src/core/hub.js
+++ b/src/core/hub.js
@@ -6,7 +6,7 @@ import ws from 'ws';
 import {Balancer} from './balancer';
 import {Config} from './config';
 import * as MiddlewareManager from './middleware';
-import {createRelay} from '../transports';
+import {createRelay} from './relay';
 import {logger} from '../utils';
 import {tcp, http, socks} from '../proxies';
 
diff --git a/src/core/relay.js b/src/core/relay.js
index 0ee34fb..cf0196d 100644
--- a/src/core/relay.js
+++ b/src/core/relay.js
@@ -1,7 +1,9 @@
 import EventEmitter from 'events';
+import uniqueId from 'lodash.uniqueid';
 import {Pipe} from './pipe';
 import {PIPE_ENCODE, PIPE_DECODE} from './middleware';
 import {CONNECT_TO_REMOTE, CONNECTION_CREATED} from '../presets';
+import {TcpInbound, TcpOutbound, TlsInbound, TlsOutbound, WsInbound, WsOutbound} from '../transports';
 
 function preparePresets() {
   let presets = __PRESETS__;
@@ -118,3 +120,17 @@ export class Relay extends EventEmitter {
   }
 
 }
+
+const mapping = {
+  'tcp': [TcpInbound, TcpOutbound],
+  'tls': [TlsInbound, TlsOutbound],
+  'ws': [WsInbound, WsOutbound]
+};
+
+export function createRelay(transport, context, proxyRequest = null) {
+  const [Inbound, Outbound] = __IS_CLIENT__ ? [TcpInbound, mapping[transport][1]] : [mapping[transport][0], TcpOutbound];
+  const props = {context, Inbound, Outbound, proxyRequest};
+  const relay = new Relay(props);
+  relay.id = uniqueId(`${transport}_`);
+  return relay;
+}
diff --git a/src/index.js b/src/index.js
index 6bb79e4..b3993a8 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,7 +1,5 @@
-import * as core from './core';
-import * as presets from './presets';
-import * as proxies from './proxies';
-import * as transports from './transports';
-import * as utils from './utils';
-
-export {core, presets, proxies, transports, utils};
+export * from './core';
+export * from './presets';
+export * from './proxies';
+export * from './transports';
+export * from './utils';
diff --git a/src/presets/defs.js b/src/presets/defs.js
index 608675a..597fb16 100644
--- a/src/presets/defs.js
+++ b/src/presets/defs.js
@@ -181,7 +181,7 @@ export class IPresetStatic extends IPreset {
  * @param clazz
  * @returns {boolean}
  */
-export function checkClass(clazz) {
+export function checkPresetClass(clazz) {
   if (typeof clazz !== 'function') {
     return false;
   }
diff --git a/src/presets/index.js b/src/presets/index.js
index cb8423e..6e65f52 100644
--- a/src/presets/index.js
+++ b/src/presets/index.js
@@ -1,4 +1,4 @@
-import {checkClass} from './defs';
+import {checkPresetClass} from './defs';
 
 // functional
 import StatsPreset from './stats';
@@ -70,7 +70,7 @@ function getPresetClassByName(name) {
     } catch (err) {
       throw Error(`cannot find preset: "${name}" from built-in modules or external: ${err.message}`);
     }
-    if (!checkClass(clazz)) {
+    if (!checkPresetClass(clazz)) {
       throw Error(`definition of preset "${name}" is invalid`);
     }
   }