diff --git a/apps/xosclient/src/main/java/org/onosproject/xosclient/impl/XosClient.java b/apps/xosclient/src/main/java/org/onosproject/xosclient/impl/XosClient.java
new file mode 100644
index 0000000..13f3aa8
--- /dev/null
+++ b/apps/xosclient/src/main/java/org/onosproject/xosclient/impl/XosClient.java
@@ -0,0 +1,170 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.xosclient.impl;
+
+import com.google.common.base.Strings;
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Modified;
+import org.apache.felix.scr.annotations.Property;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.onlab.util.Tools;
+import org.onosproject.cfg.ComponentConfigService;
+import org.onosproject.core.ApplicationId;
+import org.onosproject.core.CoreService;
+import org.onosproject.net.config.ConfigFactory;
+import org.onosproject.net.config.NetworkConfigEvent;
+import org.onosproject.net.config.NetworkConfigListener;
+import org.onosproject.net.config.NetworkConfigRegistry;
+import org.onosproject.net.config.basics.SubjectFactories;
+import org.onosproject.xosclient.api.VtnServiceApi;
+import org.onosproject.xosclient.api.XosAccess;
+import org.onosproject.xosclient.api.XosAccessConfig;
+import org.onosproject.xosclient.api.XosClientService;
+import org.osgi.service.component.ComponentContext;
+import org.slf4j.Logger;
+
+import java.util.Dictionary;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Provides interactions with XOS.
+ */
+@Component(immediate = true)
+@Service
+public class XosClient implements XosClientService {
+
+    protected final Logger log = getLogger(getClass());
+
+    private static final String VTN_BASE_URL = "vtnBaseUrl";
+    private static final String DEFAULT_VTN_BASE_URL = "/xoslib/rs/vtn/services/";
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected CoreService coreService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected ComponentConfigService componentConfigService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected NetworkConfigRegistry configRegistry;
+
+    @Property(name = VTN_BASE_URL, value = DEFAULT_VTN_BASE_URL,
+            label = "XOS VTN service API base url")
+    private String vtnBaseUrl = DEFAULT_VTN_BASE_URL;
+
+    private final ConfigFactory configFactory =
+            new ConfigFactory(SubjectFactories.APP_SUBJECT_FACTORY, XosAccessConfig.class, "xosclient") {
+                @Override
+                public XosAccessConfig createConfig() {
+                    return new XosAccessConfig();
+                }
+            };
+
+    private final NetworkConfigListener configListener = new InternalConfigListener();
+
+    private ApplicationId appId;
+    private XosAccess access = null;
+
+    @Activate
+    protected void activate(ComponentContext context) {
+        appId = coreService.registerApplication("org.onosproject.xosclient");
+
+        componentConfigService.registerProperties(getClass());
+        modified(context);
+
+        configRegistry.registerConfigFactory(configFactory);
+        configRegistry.addListener(configListener);
+
+        log.info("Started");
+    }
+
+    @Deactivate
+    protected void deactivate() {
+        log.info("Stopped");
+    }
+
+    @Modified
+    protected void modified(ComponentContext context) {
+        Dictionary<?, ?> properties = context.getProperties();
+
+        String updatedUrl = Tools.get(properties, VTN_BASE_URL);
+        if (!Strings.isNullOrEmpty(updatedUrl)) {
+            vtnBaseUrl = updatedUrl;
+        }
+
+        log.info("Modified");
+    }
+
+    @Override
+    public XosAccess access() {
+        return access;
+    }
+
+    @Override
+    public synchronized boolean setAccess(XosAccess xosAccess) {
+        checkNotNull(xosAccess);
+
+        // TODO authentication later before using the access
+        access = xosAccess;
+        return true;
+    }
+
+    @Override
+    public VtnServiceApi vtnServiceApi() {
+        checkNotNull(access, "XOS API access is not set");
+        return DefaultVtnServiceApi.getInstance(vtnBaseUrl, access);
+    }
+
+    /*
+     * adds more XOS service APIs below.
+     */
+
+    private void readConfiguration() {
+        XosAccessConfig config = configRegistry.getConfig(appId, XosAccessConfig.class);
+        if (config == null) {
+            log.debug("No configuration found");
+            return;
+        }
+
+        setAccess(config.xosAccess());
+    }
+
+    private class InternalConfigListener implements NetworkConfigListener {
+
+        @Override
+        public void event(NetworkConfigEvent event) {
+            if (!event.configClass().equals(XosAccessConfig.class)) {
+                return;
+            }
+
+            switch (event.type()) {
+                case CONFIG_ADDED:
+                case CONFIG_UPDATED:
+                    log.info("Network configuration changed");
+                    readConfiguration();
+                    break;
+                default:
+                    break;
+            }
+        }
+    }
+}