diff --git a/extras/japi/java/jvpp-common/jvpp_common.h b/extras/japi/java/jvpp-common/jvpp_common.h
index dd48138..e12141b 100644
--- a/extras/japi/java/jvpp-common/jvpp_common.h
+++ b/extras/japi/java/jvpp-common/jvpp_common.h
@@ -17,6 +17,7 @@
 //
 #include <vppinfra/types.h>
 #include <vlibapi/api.h>
+#include <vlibapi/api_types.h>
 #include <vlibmemory/api.h>
 #include <jni.h>
 
diff --git a/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/CallbackApiExample.java b/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/CallbackApiExample.java
index b99979c..b6558ff 100644
--- a/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/CallbackApiExample.java
+++ b/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/CallbackApiExample.java
@@ -77,17 +77,17 @@
             System.out.printf("Received ShowVersionReply: context=%d, program=%s, version=%s, "
                     + "buildDate=%s, buildDirectory=%s%n",
                 msg.context,
-                new String(msg.program, StandardCharsets.UTF_8),
-                new String(msg.version, StandardCharsets.UTF_8),
-                new String(msg.buildDate, StandardCharsets.UTF_8),
-                new String(msg.buildDirectory, StandardCharsets.UTF_8));
+                msg.program,
+                msg.version,
+                msg.buildDate,
+                msg.buildDirectory);
         }
 
         @Override
         public void onSwInterfaceDetails(final SwInterfaceDetails msg) {
             System.out.printf("Received SwInterfaceDetails: interfaceName=%s, l2AddressLength=%d, adminUpDown=%d, "
                     + "linkUpDown=%d, linkSpeed=%d, linkMtu=%d%n",
-                new String(msg.interfaceName, StandardCharsets.UTF_8), msg.l2AddressLength, msg.adminUpDown,
+                msg.interfaceName, msg.l2AddressLength, msg.adminUpDown,
                 msg.linkUpDown, msg.linkSpeed, (int) msg.linkMtu);
         }
 
diff --git a/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/CallbackJVppFacadeExample.java b/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/CallbackJVppFacadeExample.java
index dc2bdcb..a8b9186 100644
--- a/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/CallbackJVppFacadeExample.java
+++ b/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/CallbackJVppFacadeExample.java
@@ -39,10 +39,10 @@
         public void onShowVersionReply(final ShowVersionReply msg) {
             System.out.printf("ShowVersionCallback1 received ShowVersionReply: context=%d, program=%s,"
                     + "version=%s, buildDate=%s, buildDirectory=%s%n", msg.context,
-                new String(msg.program, StandardCharsets.UTF_8),
-                new String(msg.version, StandardCharsets.UTF_8),
-                new String(msg.buildDate, StandardCharsets.UTF_8),
-                new String(msg.buildDirectory, StandardCharsets.UTF_8));
+                msg.program,
+                msg.version,
+                msg.buildDate,
+                msg.buildDirectory);
         }
 
         @Override
@@ -57,10 +57,10 @@
         public void onShowVersionReply(final ShowVersionReply msg) {
             System.out.printf("ShowVersionCallback2 received ShowVersionReply: context=%d, program=%s,"
                     + "version=%s, buildDate=%s, buildDirectory=%s%n", msg.context,
-                new String(msg.program, StandardCharsets.UTF_8),
-                new String(msg.version, StandardCharsets.UTF_8),
-                new String(msg.buildDate, StandardCharsets.UTF_8),
-                new String(msg.buildDirectory, StandardCharsets.UTF_8));
+                msg.program,
+                msg.version,
+                msg.buildDate,
+                msg.buildDirectory);
         }
 
         @Override
diff --git a/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/FutureApiExample.java b/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/FutureApiExample.java
index 931c9b3..030e689 100644
--- a/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/FutureApiExample.java
+++ b/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/FutureApiExample.java
@@ -47,10 +47,10 @@
         LOG.info(
             String.format(
                 "Received ShowVersionReply: context=%d, program=%s, version=%s, buildDate=%s, buildDirectory=%s%n",
-                reply.context, new String(reply.program, StandardCharsets.UTF_8),
-                new String(reply.version, StandardCharsets.UTF_8),
-                new String(reply.buildDate, StandardCharsets.UTF_8),
-                new String(reply.buildDirectory, StandardCharsets.UTF_8)));
+                reply.context, reply.program,
+                reply.version,
+                reply.buildDate,
+                reply.buildDirectory));
     }
 
     private static void testEmptyBridgeDomainDump(final FutureJVppCoreFacade jvpp) throws Exception {
@@ -100,7 +100,7 @@
             LOG.info(
                 String.format("Received SwInterfaceDetails: interfaceName=%s, l2AddressLength=%d, adminUpDown=%d, "
                         + "linkUpDown=%d, linkSpeed=%d, linkMtu=%d%n",
-                    new String(details.interfaceName, StandardCharsets.UTF_8),
+                    details.interfaceName,
                     details.l2AddressLength, details.adminUpDown,
                     details.linkUpDown, details.linkSpeed, (int) details.linkMtu));
         }
diff --git a/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/L2AclExample.java b/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/L2AclExample.java
index 9a17136..0be85d4 100644
--- a/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/L2AclExample.java
+++ b/extras/japi/java/jvpp-core/io/fd/vpp/jvpp/core/examples/L2AclExample.java
@@ -75,7 +75,7 @@
             hexChars[j * 2] = hexArray[v >>> 4];
             hexChars[j * 2 + 1] = hexArray[v & 0x0F];
         }
-        return new String(hexChars);
+        return new java.lang.String(hexChars);
     }
 
     private static ClassifyTableInfo createClassifyTableInfoRequest(final int tableId) {
diff --git a/extras/japi/java/jvpp-core/jvpp_core.c b/extras/japi/java/jvpp-core/jvpp_core.c
index 09d7530..0df8589 100644
--- a/extras/japi/java/jvpp-core/jvpp_core.c
+++ b/extras/japi/java/jvpp-core/jvpp_core.c
@@ -14,7 +14,7 @@
  */
 
 #include <vnet/vnet.h>
-
+#include <jvpp-common/jvpp_common.h>
 #include <vpp/api/vpe_msg_enum.h>
 #define vl_typedefs             /* define message structures */
 #include <vpp/api/vpe_all_api_h.h>
@@ -24,8 +24,7 @@
 #include <vlibapi/api.h>
 #include <vlibmemory/api.h>
 #include <jni.h>
-
-#include <jvpp-common/jvpp_common.h>
+#include <jvpp_core.h>
 
 // TODO: generate jvpp_plugin_name.c files (or at least reuse plugin's main structure)
 typedef struct {
diff --git a/extras/japi/java/jvpp-core/jvpp_core.h b/extras/japi/java/jvpp-core/jvpp_core.h
new file mode 100644
index 0000000..bbf7a71
--- /dev/null
+++ b/extras/japi/java/jvpp-core/jvpp_core.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2018 Cisco and/or its affiliates.
+ * 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.
+ */
+
+#ifndef VPP_JVPP_CORE_H
+#define VPP_JVPP_CORE_H
+
+#include <vlibapi/api_types.h>
+
+#endif //VPP_JVPP_CORE_H
+
+// /**
+// * Host to network byte order conversion for string type. Converts String in Java to VPP string type.
+// * typedef struct
+// * {
+// *   u32 length;
+// *   u8 buf[0];
+// * } __attribute__ ((packed)) vl_api_string_t;
+// */
+static void _host_to_net_string(JNIEnv * env, jstring javaString, vl_api_string_t * _net)
+{
+    const char *nativeString = (*env)->GetStringUTFChars(env, javaString, 0);
+    int len = strlen(nativeString);
+
+    vl_api_string_t * vl_api_string = (vl_api_string_t *)calloc(1, (sizeof(vl_api_string_t) + len * sizeof(u8)));
+    if (NULL == vl_api_string)
+        return;
+
+    vl_api_string->length = len;
+    memcpy(vl_api_string->buf, nativeString, len);
+
+    _net = vl_api_string;
+    (*env)->ReleaseStringUTFChars(env, javaString, nativeString);
+}
+
+//
+// /**
+// * Network to host byte order conversion for string type. Converts VPP string type to String in Java
+// * typedef struct
+// * {
+// *   u32 length;
+// *   u8 buf[0];
+// * } __attribute__ ((packed)) vl_api_string_t;
+// */
+static jstring _net_to_host_string(JNIEnv * env, const vl_api_string_t * _net)
+{
+    jstring jstr = (*env)->NewStringUTF(env, (char *)_net->buf);
+
+    return jstr;
+}
diff --git a/extras/japi/java/jvpp/gen/jvppgen/dto_gen.py b/extras/japi/java/jvpp/gen/jvppgen/dto_gen.py
index ca015a3..cbd969d 100755
--- a/extras/japi/java/jvpp/gen/jvppgen/dto_gen.py
+++ b/extras/japi/java/jvpp/gen/jvppgen/dto_gen.py
@@ -221,7 +221,7 @@
     }
 
     @Override
-    public String toString() {
+    public java.lang.String toString() {
         return "${details_class}ReplyDump{" +
                 "${details_field}=" + ${details_field} + "}";
     }
diff --git a/extras/japi/java/jvpp/gen/jvppgen/jni_common_gen.py b/extras/japi/java/jvpp/gen/jvppgen/jni_common_gen.py
index 708cc1c..b52e5ff 100755
--- a/extras/japi/java/jvpp/gen/jvppgen/jni_common_gen.py
+++ b/extras/japi/java/jvpp/gen/jvppgen/jni_common_gen.py
@@ -165,6 +165,7 @@
     else:
         return ""
 
+
 # Make sure we do not write more elements that are expected
 _FIELD_LENGTH_CHECK = Template("""
         size_t max_size = ${field_length};
@@ -177,9 +178,13 @@
         host = field.java_name
         if not is_alias:
             net = "%s->%s" % (struct_ref_name, field.name)
-            return "    %s;" % field_type.get_host_to_net_function(host, net)
+            if field_type.name == "string":
+                net = "%s->%s" % (struct_ref_name, field.name)
+                return "    _host_to_net_%s(env, %s, (vl_api_string_t *) &%s);" % (field_type.name, host, net)
+            else:
+                return "    %s;" % field_type.get_host_to_net_function(host, net)
         else:
-            net = "%s" % (struct_ref_name)
+            net = "%s" % struct_ref_name
             return "    *%s;" % field_type.get_host_to_net_function(host, net)
     else:
         return "    %s->%s = %s;" % (struct_ref_name, field.name, field.java_name)
@@ -424,7 +429,10 @@
 def _generate_c2j_primitive_type_swap(msg_java_name, field, object_ref_name, struct_ref_name, is_alias):
     field_type = field.type
     if not is_alias:
-        template = _C2J_PRIMITIVE_TYPE_SWAP_TEMPLATE
+        if field_type.name == "string":
+            template = _C2J_STRING_TYPE_SWAP_TEMPLATE
+        else:
+            template = _C2J_PRIMITIVE_TYPE_SWAP_TEMPLATE
     else:
         template = _C2J_ALIAS_PRIMITIVE_TYPE_SWAP_TEMPLATE
     return template.substitute(
@@ -444,6 +452,12 @@
 """)
 
 
+_C2J_STRING_TYPE_SWAP_TEMPLATE = Template("""
+    jfieldID ${java_name}FieldId = (*env)->GetFieldID(env, ${class_ref_name}Class, "${java_name}", "${jni_signature}");
+    (*env)->Set${jni_accessor}Field(env, ${object_ref_name}, ${java_name}FieldId, ${net_to_host_function}(env, (const vl_api_string_t *) &${struct_ref_name}->${c_name}));
+""")
+
+
 _C2J_ALIAS_PRIMITIVE_TYPE_SWAP_TEMPLATE = Template("""
     jfieldID ${java_name}FieldId = (*env)->GetFieldID(env, ${class_ref_name}Class, "${java_name}", "${jni_signature}");
     (*env)->Set${jni_accessor}Field(env, ${object_ref_name}, ${java_name}FieldId, ${net_to_host_function}(*${struct_ref_name}));
diff --git a/extras/japi/java/jvpp/gen/jvppgen/jvpp_callback_facade_gen.py b/extras/japi/java/jvpp/gen/jvppgen/jvpp_callback_facade_gen.py
index c5634de..ebc552b 100644
--- a/extras/japi/java/jvpp/gen/jvppgen/jvpp_callback_facade_gen.py
+++ b/extras/japi/java/jvpp/gen/jvppgen/jvpp_callback_facade_gen.py
@@ -210,7 +210,7 @@
                 failedCall.onError(reply);
             } catch(RuntimeException ex) {
                 ex.addSuppressed(reply);
-                LOG.log(java.util.logging.Level.WARNING, String.format("Callback: %s failed while handling exception: %s", failedCall, reply), ex);
+                LOG.log(java.util.logging.Level.WARNING, java.lang.String.format("Callback: %s failed while handling exception: %s", failedCall, reply), ex);
             }
         }
     }
@@ -265,7 +265,7 @@
         $plugin_package.callback.$callback callback;
         final int replyId = reply.context;
         if (LOG.isLoggable(java.util.logging.Level.FINE)) {
-            LOG.fine(String.format("Received ${message} event message: %s", reply));
+            LOG.fine(java.lang.String.format("Received ${message} event message: %s", reply));
         }
         synchronized(requests) {
             callback = ($plugin_package.callback.$callback) requests.remove(replyId);
@@ -282,7 +282,7 @@
     @SuppressWarnings("unchecked")
     public void on${message}($plugin_package.dto.${message} notification) {
         if (LOG.isLoggable(java.util.logging.Level.FINE)) {
-            LOG.fine(String.format("Received ${message} event message: %s", notification));
+            LOG.fine(java.lang.String.format("Received ${message} event message: %s", notification));
         }
         eventCallback.on${message}(notification);
     }
diff --git a/extras/japi/java/jvpp/gen/jvppgen/jvpp_common_gen.py b/extras/japi/java/jvpp/gen/jvppgen/jvpp_common_gen.py
index 83226ea..499adbc 100755
--- a/extras/japi/java/jvpp/gen/jvppgen/jvpp_common_gen.py
+++ b/extras/japi/java/jvpp/gen/jvppgen/jvpp_common_gen.py
@@ -103,7 +103,7 @@
 
 _TO_STRING_TEMPLATE = Template("""
     @Override
-    public String toString() {
+    public java.lang.String toString() {
         return "$class_name{" +
 $to_string_fields
     }""")
diff --git a/extras/japi/java/jvpp/gen/jvppgen/jvpp_future_facade_gen.py b/extras/japi/java/jvpp/gen/jvppgen/jvpp_future_facade_gen.py
index 47a9985..3da367a 100644
--- a/extras/japi/java/jvpp/gen/jvppgen/jvpp_future_facade_gen.py
+++ b/extras/japi/java/jvpp/gen/jvppgen/jvpp_future_facade_gen.py
@@ -280,7 +280,7 @@
         io.fd.vpp.jvpp.future.AbstractFutureJVppInvoker.CompletableDumpFuture<$plugin_package.dto.${callback_dto}ReplyDump> completableFuture;
         final int replyId = reply.context;
         if (LOG.isLoggable(java.util.logging.Level.FINE)) {
-            LOG.fine(String.format("Received $callback_dto event message: %s", reply));
+            LOG.fine(java.lang.String.format("Received $callback_dto event message: %s", reply));
         }
         synchronized(requests) {
             completableFuture = (io.fd.vpp.jvpp.future.AbstractFutureJVppInvoker.CompletableDumpFuture<$plugin_package.dto.${callback_dto}ReplyDump>) requests.get(replyId);
@@ -305,7 +305,7 @@
         java.util.concurrent.CompletableFuture<io.fd.vpp.jvpp.dto.JVppReply<$plugin_package.dto.$request_dto>> completableFuture;
         final int replyId = reply.context;
         if (LOG.isLoggable(java.util.logging.Level.FINE)) {
-            LOG.fine(String.format("Received $callback_dto event message: %s", reply));
+            LOG.fine(java.lang.String.format("Received $callback_dto event message: %s", reply));
         }
         synchronized(requests) {
             completableFuture =
@@ -331,7 +331,7 @@
     @Override
     public void on$callback_dto($plugin_package.dto.$callback_dto notification) {
         if (LOG.isLoggable(java.util.logging.Level.FINE)) {
-            LOG.fine(String.format("Received $callback_dto event message: %s", notification));
+            LOG.fine(java.lang.String.format("Received $callback_dto event message: %s", notification));
         }
         notificationCallback.on$callback_dto(notification);
     }
diff --git a/extras/japi/java/jvpp/gen/jvppgen/jvpp_impl_gen.py b/extras/japi/java/jvpp/gen/jvppgen/jvpp_impl_gen.py
index aff8d7f..376952b 100755
--- a/extras/japi/java/jvpp/gen/jvppgen/jvpp_impl_gen.py
+++ b/extras/japi/java/jvpp/gen/jvppgen/jvpp_impl_gen.py
@@ -74,7 +74,7 @@
 public final class JVpp${plugin_name}Impl implements $plugin_package.JVpp${plugin_name} {
 
     private final static Logger LOG = Logger.getLogger(JVpp${plugin_name}Impl.class.getName());
-    private static final String LIBNAME = "libjvpp_${plugin_name_underscore}.so";
+    private static final java.lang.String LIBNAME = "libjvpp_${plugin_name_underscore}.so";
 
     // FIXME using NativeLibraryLoader makes load fail could not find (WantInterfaceEventsReply).
     static {
@@ -151,7 +151,7 @@
         java.util.Objects.requireNonNull(request, "Null request object");
         connection.checkActive();
         if (LOG.isLoggable(Level.FINE)) {
-            LOG.fine(String.format("Sending $type event message: %s", request));
+            LOG.fine(java.lang.String.format("Sending $type event message: %s", request));
         }
         int result=${name}0(request);
         if (result<0){
diff --git a/extras/japi/java/jvpp/gen/jvppgen/jvpp_model.py b/extras/japi/java/jvpp/gen/jvppgen/jvpp_model.py
index 1609968..da1e01f 100755
--- a/extras/japi/java/jvpp/gen/jvppgen/jvpp_model.py
+++ b/extras/japi/java/jvpp/gen/jvppgen/jvpp_model.py
@@ -92,9 +92,11 @@
 
 # TODO(VPP-1187): add array host to net functions to reduce number of members and simplify JNI generation
 class Array(Type):
-    def __init__(self, base_type):
+    def __init__(self, base_type, name=None):
+        if name is None:
+            name = base_type.name + _ARRAY_SUFFIX
         super(Array, self).__init__(
-            name=base_type.name + _ARRAY_SUFFIX,
+            name=name,
             java_name=base_type.java_name + _ARRAY_SUFFIX,
             java_name_fqn=base_type.java_name_fqn + _ARRAY_SUFFIX,
             jni_signature="[%s" % base_type.jni_signature,
@@ -341,6 +343,8 @@
         self._parse_types(types)
 
     def _parse_aliases(self, types):
+
+        # model aliases
         for alias_name in self._aliases:
             alias = self._aliases[alias_name]
             alias_type = {"type": "type"}
@@ -442,7 +446,10 @@
             'i64': SimpleType('i64', 'long', 'J', 'jlong', 'Long',
                               host_to_net_function='clib_host_to_net_i64',
                               net_to_host_function='clib_net_to_host_i64'),
-            'f64': SimpleType('f64', 'double', 'D', 'jdouble', 'Double')
+            'f64': SimpleType('f64', 'double', 'D', 'jdouble', 'Double'),
+            'string': SimpleType('string', 'String', 'l', 'jstring', 'Object',
+                                 host_to_net_function='_host_to_net_string',
+                                 net_to_host_function='_net_to_host_string')
         })
 
         for n, t in self._types_by_name.items():
diff --git a/extras/japi/java/jvpp/gen/jvppgen/notification_gen.py b/extras/japi/java/jvpp/gen/jvppgen/notification_gen.py
index 69e870e..fa86fe4 100644
--- a/extras/japi/java/jvpp/gen/jvppgen/notification_gen.py
+++ b/extras/japi/java/jvpp/gen/jvppgen/notification_gen.py
@@ -117,7 +117,7 @@
     public void on$notification(
         final $plugin_package.dto.$notification notification) {
         if (LOG.isLoggable(java.util.logging.Level.FINE)) {
-            LOG.fine(String.format("Received $notification event message: %s", notification));
+            LOG.fine(java.lang.String.format("Received $notification event message: %s", notification));
         }
         final io.fd.vpp.jvpp.callback.JVppCallback jVppCallback = registeredCallbacks.get($plugin_package.dto.$notification.class);
         if (null != jVppCallback) {
@@ -153,7 +153,7 @@
     @Override
     public void onError(io.fd.vpp.jvpp.VppCallbackException ex) {
         java.util.logging.Logger LOG = java.util.logging.Logger.getLogger(${plugin_name}EventRegistryImpl.class.getName());
-        LOG.log(java.util.logging.Level.WARNING, String.format("Received onError exception: call=%s, context=%d, retval=%d%n", ex.getMethodName(),
+        LOG.log(java.util.logging.Level.WARNING, java.lang.String.format("Received onError exception: call=%s, context=%d, retval=%d%n", ex.getMethodName(),
             ex.getCtxId(), ex.getErrorCode()), ex);
     }
 }
diff --git a/src/tools/vppapigen/vppapigen_c.py b/src/tools/vppapigen/vppapigen_c.py
index f0fb008..e189b02 100644
--- a/src/tools/vppapigen/vppapigen_c.py
+++ b/src/tools/vppapigen/vppapigen_c.py
@@ -3,7 +3,8 @@
 import os
 import time
 
-datestring = datetime.datetime.utcfromtimestamp(int(os.environ.get('SOURCE_DATE_EPOCH', time.time())))
+datestring = datetime.datetime.utcfromtimestamp(
+    int(os.environ.get('SOURCE_DATE_EPOCH', time.time())))
 input_filename = 'inputfil'
 top_boilerplate = '''\
 /*
@@ -94,6 +95,13 @@
     return '#endif\n\n'
 
 
+def api2c(fieldtype):
+    mappingtable = {'string': 'vl_api_string_t', }
+    if fieldtype in mappingtable:
+        return mappingtable[fieldtype]
+    return fieldtype
+
+
 def typedefs(objs, aliases, filename):
     name = filename.replace('.', '_')
     output = '''\
@@ -130,12 +138,12 @@
                 output += "typedef VL_API_PACKED(struct _vl_api_%s {\n" % o.name
             for b in o.block:
                 if b.type == 'Field':
-                    output += "    %s %s;\n" % (b.fieldtype, b.fieldname)
+                    output += "    %s %s;\n" % (api2c(b.fieldtype), b.fieldname)
                 elif b.type == 'Array':
                     if b.lengthfield:
-                        output += "    %s %s[0];\n" % (b.fieldtype, b.fieldname)
+                        output += "    %s %s[0];\n" % (api2c(b.fieldtype), b.fieldname)
                     else:
-                        output += "    %s %s[%s];\n" % (b.fieldtype, b.fieldname,
+                        output += "    %s %s[%s];\n" % (api2c(b.fieldtype), b.fieldname,
                                                         b.length)
                 else:
                     raise ValueError("Error in processing array type %s" % b)
diff --git a/src/tools/vppapigen/vppapigen_json.py b/src/tools/vppapigen/vppapigen_json.py
index b57e16c..a4707c0 100644
--- a/src/tools/vppapigen/vppapigen_json.py
+++ b/src/tools/vppapigen/vppapigen_json.py
@@ -32,19 +32,18 @@
         d = []
         d.append(t.name)
         for b in t.block:
-            f = []
             if b.type == 'Field':
-                f = [b.fieldtype, b.fieldname]
+                d.append([b.fieldtype, b.fieldname])
             elif b.type == 'Array':
                 if b.lengthfield:
-                    f = [b.fieldtype, b.fieldname, b.length, b.lengthfield]
+                    d.append([b.fieldtype, b.fieldname, b.length, b.lengthfield])
                 else:
-                    f = [b.fieldtype, b.fieldname, b.length]
+                    d.append([b.fieldtype, b.fieldname, b.length])
             elif b.type == 'Union':
-                print('UNION')
+                pass
             else:
                 raise ValueError("Error in processing array type %s" % b)
-            d.append(f)
+
         if t.crc:
             c = {}
             c['crc'] = "{0:#0{1}x}".format(t.crc, 10)
diff --git a/src/vat/api_format.c b/src/vat/api_format.c
index 7f4dabe..25d2dd3 100644
--- a/src/vat/api_format.c
+++ b/src/vat/api_format.c
@@ -1105,7 +1105,7 @@
 {
   vat_main_t *vam = &vat_main;
   i32 retval = ntohl (mp->retval);
-  u32 length = ntohl (mp->length);
+  u32 length = vl_api_string_len (&mp->reply);
 
   vec_reset_length (vam->cmd_reply);
 
@@ -1113,7 +1113,8 @@
   if (retval == 0)
     {
       vec_validate (vam->cmd_reply, length);
-      clib_memcpy ((char *) (vam->cmd_reply), mp->reply, length);
+      clib_memcpy ((char *) (vam->cmd_reply),
+		   vl_api_from_api_string (&mp->reply), length);
       vam->cmd_reply[length] = 0;
     }
   vam->result_ready = 1;
@@ -1129,7 +1130,8 @@
 
   vat_json_init_object (&node);
   vat_json_object_add_int (&node, "retval", ntohl (mp->retval));
-  vat_json_object_add_string_copy (&node, "reply", mp->reply);
+  vat_json_object_add_string_copy (&node, "reply",
+				   vl_api_from_api_string (&mp->reply));
 
   vat_json_print (vam->ofp, &node);
   vat_json_free (&node);
@@ -1300,10 +1302,18 @@
 
   if (retval >= 0)
     {
-      errmsg ("        program: %s", mp->program);
-      errmsg ("        version: %s", mp->version);
-      errmsg ("     build date: %s", mp->build_date);
-      errmsg ("build directory: %s", mp->build_directory);
+      char *p = (char *) &mp->program;
+      errmsg ("        program: %s\n",
+	      vl_api_from_api_string ((vl_api_string_t *) p));
+      p += vl_api_string_len ((vl_api_string_t *) p) + sizeof (u32);
+      errmsg ("        version: %s\n",
+	      vl_api_from_api_string ((vl_api_string_t *) p));
+      p += vl_api_string_len ((vl_api_string_t *) p) + sizeof (u32);
+      errmsg ("     build date: %s\n",
+	      vl_api_from_api_string ((vl_api_string_t *) p));
+      p += vl_api_string_len ((vl_api_string_t *) p) + sizeof (u32);
+      errmsg ("build directory: %s\n",
+	      vl_api_from_api_string ((vl_api_string_t *) p));
     }
   vam->retval = retval;
   vam->result_ready = 1;
@@ -1317,11 +1327,22 @@
 
   vat_json_init_object (&node);
   vat_json_object_add_int (&node, "retval", ntohl (mp->retval));
-  vat_json_object_add_string_copy (&node, "program", mp->program);
-  vat_json_object_add_string_copy (&node, "version", mp->version);
-  vat_json_object_add_string_copy (&node, "build_date", mp->build_date);
+  char *p = (char *) &mp->program;
+  vat_json_object_add_string_copy (&node, "program",
+				   vl_api_from_api_string ((vl_api_string_t *)
+							   p));
+  p += vl_api_string_len ((vl_api_string_t *) p) + sizeof (u32);
+  vat_json_object_add_string_copy (&node, "version",
+				   vl_api_from_api_string ((vl_api_string_t *)
+							   p));
+  p += vl_api_string_len ((vl_api_string_t *) p) + sizeof (u32);
+  vat_json_object_add_string_copy (&node, "build_date",
+				   vl_api_from_api_string ((vl_api_string_t *)
+							   p));
+  p += vl_api_string_len ((vl_api_string_t *) p) + sizeof (u32);
   vat_json_object_add_string_copy (&node, "build_directory",
-				   mp->build_directory);
+				   vl_api_from_api_string ((vl_api_string_t *)
+							   p));
 
   vat_json_print (vam->ofp, &node);
   vat_json_free (&node);
@@ -6339,8 +6360,7 @@
    */
   u32 len = vec_len (vam->input->buffer);
   M2 (CLI_INBAND, mp, len);
-  clib_memcpy (mp->cmd, vam->input->buffer, len);
-  mp->length = htonl (len);
+  vl_api_to_api_string (len, (const char *) vam->input->buffer, &mp->cmd);
 
   S (mp);
   W (ret);
diff --git a/src/vlibapi/CMakeLists.txt b/src/vlibapi/CMakeLists.txt
index 55f87b8..dfd6b5b 100644
--- a/src/vlibapi/CMakeLists.txt
+++ b/src/vlibapi/CMakeLists.txt
@@ -17,6 +17,7 @@
   api.h
   vat_helper_macros.h
   api_common.h
+  api_types.h
 
   DESTINATION
   include/vlibapi
diff --git a/src/vlibapi/api_common.h b/src/vlibapi/api_common.h
index 497a1e8..735921b 100644
--- a/src/vlibapi/api_common.h
+++ b/src/vlibapi/api_common.h
@@ -25,6 +25,7 @@
  */
 
 #include <vppinfra/clib_error.h>
+#include <vlibapi/api_types.h>
 #include <svm/svm_common.h>
 #include <svm/queue.h>
 
diff --git a/src/vlibapi/api_types.h b/src/vlibapi/api_types.h
new file mode 100644
index 0000000..759298e
--- /dev/null
+++ b/src/vlibapi/api_types.h
@@ -0,0 +1,54 @@
+/*
+ *------------------------------------------------------------------
+ * api_types.h
+ *
+ * Copyright (c) 2018 Cisco and/or its affiliates.
+ * 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.
+ *------------------------------------------------------------------
+ */
+
+#ifndef included_api_types_h
+#define included_api_types_h
+
+#include <vppinfra/types.h>
+
+/* VPP API string type */
+typedef struct
+{
+  u32 length;
+  u8 buf[0];
+} __attribute__ ((packed)) vl_api_string_t;
+
+static inline int
+vl_api_to_api_string (u32 len, const char *buf, vl_api_string_t * str)
+{
+  if (strncpy_s ((char *) str->buf, len, buf, len - 1) != 0)
+    len = 0;
+  str->length = clib_host_to_net_u32 (len);
+  return len + sizeof (u32);
+}
+
+/* Return a C string from API string */
+static inline u8 *
+vl_api_from_api_string (vl_api_string_t * astr)
+{
+  return astr->buf;
+}
+
+static inline u32
+vl_api_string_len (vl_api_string_t * astr)
+{
+  return clib_net_to_host_u32 (astr->length);
+}
+
+#endif
diff --git a/src/vpp-api/python/vpp_papi/vpp_papi.py b/src/vpp-api/python/vpp_papi/vpp_papi.py
index 32abe14..4de257c 100644
--- a/src/vpp-api/python/vpp_papi/vpp_papi.py
+++ b/src/vpp-api/python/vpp_papi/vpp_papi.py
@@ -29,6 +29,8 @@
 from . vpp_serializer import VPPType, VPPEnumType, VPPUnionType, BaseTypes
 from . vpp_serializer import VPPMessage, vpp_get_type, VPPTypeAlias
 
+logger = logging.getLogger(__name__)
+
 if sys.version[0] == '2':
     import Queue as queue
 else:
@@ -63,6 +65,19 @@
         return d.items()
 
 
+def call_logger(msgdef, kwargs):
+    s = 'Calling {}('.format(msgdef.name)
+    for k, v in kwargs.items():
+        s += '{}:{} '.format(k, v)
+    s += ')'
+    return s
+
+
+def return_logger(r):
+    s = 'Return from {}'.format(r)
+    return s
+
+
 class VppApiDynamicMethodHolder(object):
     pass
 
@@ -493,10 +508,31 @@
         else:
             raise VPPIOError(2, 'RPC reply message received in event handler')
 
+    def has_context(self, msg):
+        if len(msg) < 10:
+            return False
+
+        header = VPPType('header_with_context', [['u16', 'msgid'],
+                                                 ['u32', 'client_index'],
+                                                 ['u32', 'context']])
+
+        (i, ci, context), size = header.unpack(msg, 0)
+        if self.id_names[i] == 'rx_thread_exit':
+            return
+
+        #
+        # Decode message and returns a tuple.
+        #
+        msgobj = self.id_msgdef[i]
+        if 'context' in msgobj.field_by_name and context >= 0:
+            return True
+        return False
+
     def decode_incoming_msg(self, msg, no_type_conversion=False):
         if not msg:
             self.logger.warning('vpp_api.read failed')
             return
+
         (i, ci), size = self.header.unpack(msg, 0)
         if self.id_names[i] == 'rx_thread_exit':
             return
@@ -537,7 +573,7 @@
             raise VPPValueError('Invalid argument {} to {}'
                                 .format(list(d), msg.name))
 
-    def _call_vpp(self, i, msg, multipart, **kwargs):
+    def _call_vpp(self, i, msgdef, multipart, **kwargs):
         """Given a message, send the message and await a reply.
 
         msgdef - the message packing definition
@@ -567,8 +603,11 @@
                 kwargs['client_index'] = self.transport.socket_index
         except AttributeError:
             pass
-        self.validate_args(msg, kwargs)
-        b = msg.pack(kwargs)
+        self.validate_args(msgdef, kwargs)
+
+        logging.debug(call_logger(msgdef, kwargs))
+
+        b = msgdef.pack(kwargs)
         self.transport.suspend()
 
         self.transport.write(b)
@@ -601,6 +640,7 @@
 
         self.transport.resume()
 
+        logger.debug(return_logger(rl))
         return rl
 
     def _call_vpp_async(self, i, msg, **kwargs):
diff --git a/src/vpp-api/python/vpp_papi/vpp_serializer.py b/src/vpp-api/python/vpp_papi/vpp_serializer.py
index 5dce03b..418c024 100644
--- a/src/vpp-api/python/vpp_papi/vpp_serializer.py
+++ b/src/vpp-api/python/vpp_papi/vpp_serializer.py
@@ -59,6 +59,7 @@
 class BaseTypes(object):
     def __init__(self, type, elements=0):
         base_types = {'u8': '>B',
+                      'string': '>s',
                       'u16': '>H',
                       'u32': '>I',
                       'i32': '>i',
@@ -67,13 +68,11 @@
                       'bool': '>?',
                       'header': '>HI'}
 
-        if elements > 0 and type == 'u8':
+        if elements > 0 and (type == 'u8' or type == 'string'):
             self.packer = struct.Struct('>%ss' % elements)
         else:
             self.packer = struct.Struct(base_types[type])
         self.size = self.packer.size
-        logger.debug('Adding {} with format: {}'
-                     .format(type, base_types[type]))
 
     def pack(self, data, kwargs=None):
         if not data:  # Default to zero if not specified
@@ -84,10 +83,32 @@
         return self.packer.unpack_from(data, offset)[0], self.packer.size
 
 
+class String(object):
+    def __init__(self):
+        self.name = 'string'
+        self.size = 1
+        self.length_field_packer = BaseTypes('u32')
+
+    def pack(self, list, kwargs=None):
+        if not list:
+            return self.length_field_packer.pack(0) + b""
+        return self.length_field_packer.pack(len(list)) + list.encode('utf8')
+
+    def unpack(self, data, offset=0, result=None, ntc=False):
+        length, length_field_size = self.length_field_packer.unpack(data,
+                                                                    offset)
+        if length == 0:
+            return b'', 0
+        p = BaseTypes('u8', length)
+        x, size = p.unpack(data, offset + length_field_size)
+        x2 = x.split(b'\0',1)[0]
+        return (x2.decode('utf8'), size + length_field_size)
+
+
 types = {'u8': BaseTypes('u8'), 'u16': BaseTypes('u16'),
          'u32': BaseTypes('u32'), 'i32': BaseTypes('i32'),
          'u64': BaseTypes('u64'), 'f64': BaseTypes('f64'),
-         'bool': BaseTypes('bool')}
+         'bool': BaseTypes('bool'), 'string': String()}
 
 
 def vpp_get_type(name):
@@ -107,6 +128,7 @@
         self.num = num
         self.packer = BaseTypes(field_type, num)
         self.size = self.packer.size
+        self.field_type = field_type
 
     def pack(self, data, kwargs=None):
         """Packs a fixed length bytestring. Left-pads with zeros
@@ -128,6 +150,10 @@
                 'Invalid array length for "{}" got {}'
                 ' expected {}'
                 .format(self.name, len(data[offset:]), self.num))
+        if self.field_type == 'string':
+            s = self.packer.unpack(data, offset)
+            s2 = s[0].split(b'\0', 1)[0]
+            return (s2.decode('utf-8'), self.num)
         return self.packer.unpack(data, offset)
 
 
@@ -164,6 +190,7 @@
 class VLAList(object):
     def __init__(self, name, field_type, len_field_name, index):
         self.name = name
+        self.field_type = field_type
         self.index = index
         self.packer = types[field_type]
         self.size = self.packer.size
@@ -179,6 +206,7 @@
         b = bytes()
 
         # u8 array
+
         if self.packer.size == 1:
             return bytearray(list)
 
@@ -249,7 +277,6 @@
             e_hash[ename] = evalue
         self.enum = IntEnum(name, e_hash)
         types[name] = self
-        logger.debug('Adding enum {}'.format(name))
 
     def __getattr__(self, name):
         return self.enum[name]
@@ -290,7 +317,6 @@
 
         types[name] = self
         self.tuple = collections.namedtuple(name, fields, rename=True)
-        logger.debug('Adding union {}'.format(name))
 
     # Union of variable length?
     def pack(self, data, kwargs=None):
@@ -381,7 +407,7 @@
                 if list_elements == 0:
                     p = VLAList_legacy(f_name, f_type)
                     self.packers.append(p)
-                elif f_type == 'u8':
+                elif f_type == 'u8' or f_type == 'string':
                     p = FixedList_u8(f_name, f_type, list_elements)
                     self.packers.append(p)
                     size += p.size
@@ -390,10 +416,9 @@
                     self.packers.append(p)
                     size += p.size
             elif len(f) == 4:  # Variable length list
-                    # Find index of length field
-                    length_index = self.fields.index(f[3])
-                    p = VLAList(f_name, f_type, f[3], length_index)
-                    self.packers.append(p)
+                length_index = self.fields.index(f[3])
+                p = VLAList(f_name, f_type, f[3], length_index)
+                self.packers.append(p)
             else:
                 self.packers.append(types[f_type])
                 size += types[f_type].size
@@ -401,7 +426,6 @@
         self.size = size
         self.tuple = collections.namedtuple(name, self.fields, rename=True)
         types[name] = self
-        logger.debug('Adding type {}'.format(name))
 
     def pack(self, data, kwargs=None):
         if not kwargs:
diff --git a/src/vpp-api/python/vpp_papi/vpp_transport_socket.py b/src/vpp-api/python/vpp_papi/vpp_transport_socket.py
index 393e2e9..4341cad 100644
--- a/src/vpp-api/python/vpp_papi/vpp_transport_socket.py
+++ b/src/vpp-api/python/vpp_papi/vpp_transport_socket.py
@@ -59,8 +59,7 @@
                         return
                     # Put either to local queue or if context == 0
                     # callback queue
-                    r = self.parent.decode_incoming_msg(msg)
-                    if hasattr(r, 'context') and r.context > 0:
+                    if self.parent.has_context(msg):
                         self.q.put(msg)
                     else:
                         self.parent.msg_handler_async(msg)
diff --git a/src/vpp/api/api.c b/src/vpp/api/api.c
index cf5d252..1f376dc 100644
--- a/src/vpp/api/api.c
+++ b/src/vpp/api/api.c
@@ -217,16 +217,25 @@
   vlib_main_t *vm = vlib_get_main ();
   unformat_input_t input;
   u8 *out_vec = 0;
+  u32 len = 0;
 
-  unformat_init_string (&input, (char *) mp->cmd, ntohl (mp->length));
+  if (vl_msg_api_get_msg_length (mp) < vl_api_string_len (&mp->cmd))
+    {
+      rv = -1;
+      goto error;
+    }
+
+  unformat_init_string (&input, (char *) vl_api_from_api_string (&mp->cmd),
+			vl_api_string_len (&mp->cmd));
   vlib_cli_input (vm, &input, inband_cli_output, (uword) & out_vec);
 
-  u32 len = vec_len (out_vec);
+  len = vec_len (out_vec);
+
+error:
   /* *INDENT-OFF* */
   REPLY_MACRO3(VL_API_CLI_INBAND_REPLY, len,
   ({
-    rmp->length = htonl (len);
-    clib_memcpy (rmp->reply, out_vec, len);
+    vl_api_to_api_string(len, (const char *)out_vec, &rmp->reply);
   }));
   /* *INDENT-ON* */
   vec_free (out_vec);
@@ -241,16 +250,22 @@
   char *vpe_api_get_version (void);
   char *vpe_api_get_build_date (void);
 
+  u32 program_len = strnlen_s ("vpe", 32) + 1;
+  u32 version_len = strnlen_s (vpe_api_get_version (), 32) + 1;
+  u32 build_date_len = strnlen_s (vpe_api_get_build_date (), 32) + 1;
+  u32 build_directory_len =
+    strnlen_s (vpe_api_get_build_directory (), 256) + 1;
+
+  u32 n = program_len + version_len + build_date_len + build_directory_len;
+
   /* *INDENT-OFF* */
-  REPLY_MACRO2(VL_API_SHOW_VERSION_REPLY,
+  REPLY_MACRO3(VL_API_SHOW_VERSION_REPLY, n,
   ({
-    strncpy ((char *) rmp->program, "vpe", ARRAY_LEN(rmp->program)-1);
-    strncpy ((char *) rmp->build_directory, vpe_api_get_build_directory(),
-             ARRAY_LEN(rmp->build_directory)-1);
-    strncpy ((char *) rmp->version, vpe_api_get_version(),
-             ARRAY_LEN(rmp->version)-1);
-    strncpy ((char *) rmp->build_date, vpe_api_get_build_date(),
-             ARRAY_LEN(rmp->build_date)-1);
+    char *p = (char *)&rmp->program;
+    p += vl_api_to_api_string(program_len, "vpe", (vl_api_string_t *)p);
+    p += vl_api_to_api_string(version_len, vpe_api_get_version(), (vl_api_string_t *)p);
+    p += vl_api_to_api_string(build_date_len, vpe_api_get_build_date(), (vl_api_string_t *)p);
+    vl_api_to_api_string(build_directory_len, vpe_api_get_build_directory(), (vl_api_string_t *)p);
   }));
   /* *INDENT-ON* */
 }
diff --git a/src/vpp/api/custom_dump.c b/src/vpp/api/custom_dump.c
index 41a24ef..78d3704 100644
--- a/src/vpp/api/custom_dump.c
+++ b/src/vpp/api/custom_dump.c
@@ -2109,10 +2109,10 @@
 {
   u8 *s;
   u8 *cmd = 0;
-  u32 length = ntohl (mp->length);
+  u32 length = vl_api_string_len (&mp->cmd);
 
   vec_validate (cmd, length);
-  clib_memcpy (cmd, mp->cmd, length);
+  clib_memcpy (cmd, vl_api_from_api_string (&mp->cmd), length);
 
   s = format (0, "SCRIPT: exec %v ", cmd);
 
diff --git a/src/vpp/api/types.h b/src/vpp/api/types.h
index 252caa2..9a45639 100644
--- a/src/vpp/api/types.h
+++ b/src/vpp/api/types.h
@@ -16,6 +16,9 @@
 #ifndef __API_TYPES_H__
 #define __API_TYPES_H__
 
+#include <vlibapi/api_common.h>
+#include <vlibapi/api_types.h>
+
 #define vl_typedefs		/* define message structures */
 #include <vpp/api/vpe_all_api_h.h>
 #undef vl_typedefs
diff --git a/src/vpp/api/vpe.api b/src/vpp/api/vpe.api
index 488af17..24d44bd 100644
--- a/src/vpp/api/vpe.api
+++ b/src/vpp/api/vpe.api
@@ -93,8 +93,7 @@
 {
   u32 client_index;
   u32 context;
-  u32 length;
-  u8 cmd[length];
+  string cmd;
 };
 
 /** \brief vpe parser cli string response
@@ -112,8 +111,7 @@
 {
   u32 context;
   i32 retval;
-  u32 length;
-  u8 reply[length];
+  string reply;
 };
 
 /** \brief Get node index using name request
@@ -187,10 +185,10 @@
 {
   u32 context;
   i32 retval;
-  u8 program[32];
-  u8 version[32];
-  u8 build_date[32];
-  u8 build_directory[256];
+  string program;
+  string version;
+  string build_date;
+  string build_directory;
 };
 
 
diff --git a/test/framework.py b/test/framework.py
index 242a079..f82f075 100644
--- a/test/framework.py
+++ b/test/framework.py
@@ -918,7 +918,7 @@
     def assert_packet_counter_equal(self, counter, expected_value):
         counters = self.vapi.cli("sh errors").split('\n')
         counter_value = -1
-        for i in range(1, len(counters) - 1):
+        for i in range(1, len(counters)):
             results = counters[i].split()
             if results[1] == counter:
                 counter_value = int(results[0])
diff --git a/test/vpp_papi_provider.py b/test/vpp_papi_provider.py
index 320ea12..4812cb6 100644
--- a/test/vpp_papi_provider.py
+++ b/test/vpp_papi_provider.py
@@ -210,10 +210,10 @@
         """
         self.hook.before_cli(cli)
         cli += '\n'
-        r = self.papi.cli_inband(length=len(cli), cmd=str(cli).encode('utf8'))
+        r = self.papi.cli_inband(cmd=cli)
         self.hook.after_cli(cli)
         if hasattr(r, 'reply'):
-            return r.reply.decode().rstrip('\x00')
+            return r.reply
 
     def ppcli(self, cli):
         """ Helper method to print CLI command in case of info logging level.