diff --git a/client/client.js b/client/client.js
index 2b11fd9..41ea82e 100644
--- a/client/client.js
+++ b/client/client.js
@@ -1,7 +1,8 @@
-'use strict';
 //-- vim: ft=javascript tabstop=2 softtabstop=2 expandtab shiftwidth=2
+'use strict';
 const path = require('path');
 const http = require('http');
+const checksum = require('../lib').checksum;
 const WebSocket = require('ws');
 const WsJsonProtocol = require('../lib/ws-json');
 
@@ -36,8 +37,11 @@ class RequestForwarder extends Object {
         let _send = this._send.bind(this);
         let sender = function sender(event_id) {
           return function (data) {
-            if (event_id != 'data') 
+            if (event_id == 'data') {
+              console.log(`<:  ${message.channel}:  ${event_id} ${ireq.method} ${oreq_uri.pathname} ${data.length} ${checksum(data)}`);
+            } else {
               console.log(`<:  ${message.channel}:  ${event_id} ${ireq.method} ${oreq_uri.pathname}`);
+            }
             _send({
               channel: message.channel,
               id: message.id,
@@ -48,7 +52,7 @@ class RequestForwarder extends Object {
         }
         console.log(` :> ${message.channel}:  ${ireq.method} ${oreq_uri.toString()}`);
         req = http.request(oreq_uri.toString(), req_params, function handleResponse(res) {
-          res.setEncoding('utf8');
+          // res.setEncoding('utf8');
           console.log(`<:  ${message.channel}:  ${res.statusCode} ${res.statusMessage} / ${ireq.method} ${oreq_uri.pathname}`);
           sender('headers')({
             statusCode: res.statusCode,
@@ -65,7 +69,9 @@ class RequestForwarder extends Object {
         req = this._activeChannels[message.channel];
         if (req) {
             try {
-                console.log(`  :> DATA[${message.data}]`);
+                if (message.data instanceof Object) {
+                    message.data = Buffer.from(message.data);
+                console.log(`  :> ${digest(message.data)}]`);
                 req.write(message.data);
             } catch(err) {
                 console.log('data is object', message);
diff --git a/lib/index.js b/lib/index.js
index e69de29..e249d47 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -0,0 +1,16 @@
+//-- vim: ft=javascript tabstop=2 softtabstop=2 expandtab shiftwidth=2
+'use strict';
+
+const crypto = require('crypto');
+
+function checksum(data, {length=5}={}) {
+  try {
+    return crypto.createHash('md5').update(data).digest('hex').slice(0,length).replace(/(.{4})/g, ':$1').slice(1);
+  } catch(err) {
+    console.error(err, data);
+    throw err;
+  }
+}
+
+exports.checksum = checksum;
+module.exports.WsJsonProtocol = require('./ws-json').WsJsonProtocol;
diff --git a/server/api.js b/server/api.js
index 1473c68..8ef58a5 100644
--- a/server/api.js
+++ b/server/api.js
@@ -1,6 +1,7 @@
 'use strict';
 //-- vim: ft=javascript tabstop=2 softtabstop=2 expandtab shiftwidth=2
 const REQ_SIZE_LIMIT = 1024*1024;
+const checksum = require('../lib').checksum;
 const uuid = require('uuid');
 const { HttpError, BadGateway, NotFound } = require('./HttpError');
 
@@ -27,12 +28,17 @@ class ForwardedRequest extends Object {
   }
 
   on_headers(message) {
-      console.log(`<:   ${this.channelUrl}:  ${message.data.statusCode} ${message.data.statusMessage} / ${message.event} ${this.request.method} ${this.request.url}`);
+      console.log(`<:   ${this.channelUrl}:  ${message.data.statusCode} ${message.data.statusMessage}
+        ${JSON.stringify(message.data.headers)}
+        / ${message.event} ${this.request.method} ${this.request.url}`);
       this.response.writeHead(message.data.statusCode, message.data.statusMessage, message.data.headers);
   }
 
   on_data(message) {
-      // console.log(`<:   ${this.channelUrl}:  data ${message.data.length}`);
+      if (message.data instanceof Object) {
+        message.data = Buffer.from(message.data)
+      }
+      console.log(`<:   ${this.channelUrl}:  data ${checksum(message.data)}`);
       this.response.write(message.data);
   }
 
@@ -60,8 +66,8 @@ class ForwardedRequest extends Object {
   }
 
   resendDataChunk(chunk) {
-    console.log(`  :> ${this.channelUrl} data`);
-    this.sendMessage('data', chunk.toString());
+    console.log(`  :> ${this.channelUrl} data${checksum(chunk)}`);
+    this.sendMessage('data', chunk.toString()); // FIXME: is it binary safe?
   }
 
   resendError(error) {