diff --git a/.gitignore b/.gitignore
index 7033506..4ba957c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,6 @@
+Makefile.rules
+config.h
+testmodbus-client
 .project
 testmodbus-client.ui~
 *.oo
diff --git a/Makefile b/Makefile
index 707e1de..601649d 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@ VERSION = 1.0.1
 
 -include Makefile.rules
 
-OBJECTSCLI = client.oo tcp.oo nwthread.oo
+OBJECTSCLI = client.oo tcp.oo nwthread.oo modbus.oo
 
 DISTNAME=testmodbus-client-$(VERSION)
 
diff --git a/modbus.cc b/modbus.cc
new file mode 100644
index 0000000..dfc100a
--- /dev/null
+++ b/modbus.cc
@@ -0,0 +1,88 @@
+/////////////////////////////////////////////////////////////////////////////////
+//
+// modbus.cc is part of TestModbus-Client.
+//
+/////////////////////////////////////////////////////////////////////////////////
+
+#include <string.h>
+#include <errno.h>
+#include "modbus.h"
+
+#define PACK_INT8(__dstptr, __srci8)					\
+	memcpy(__dstptr, &__srci8, 1); 						\
+	__dstptr += 1
+
+#define UNPACK_INT8(__dsti8, __srcptr)					\
+	memcpy(&__dsti8, __srcptr, 1); 						\
+	__srcptr += 1
+
+#define PACK_INT16(__tmpi16, __dstptr, __srci16) 		\
+	__tmpi16 = htons((uint16_t)__srci16); 				\
+	memcpy(__dstptr, &__tmpi16, 2); 					\
+	__dstptr += 2
+
+#define UNPACK_INT16(__tmpi16, __dsti16, __srcptr) 		\
+	memcpy(&__tmpi16, __srcptr, 2);						\
+	__srcptr += 2; 										\
+	__dsti16 = ntohs((uint16_t)__tmpi16)
+
+/*
+ * packs the header into the buffer data and returns the lenght of the header
+ * returns NULL on error or points to end of data
+ */
+char * modbustcp_pkt_header (char *destbuffer, int bufsize, modbustcp_header *srcmbh) {
+	uint16_t tmp;
+
+	// destination memory valid
+	if (destbuffer == NULL) {
+		errno = EFAULT;
+		return NULL;
+	}
+	if (bufsize < 12) {
+		errno = EOVERFLOW;
+		return NULL;
+	}
+
+	char *pos = destbuffer;
+
+	PACK_INT16(tmp, pos, srcmbh->transid);
+	PACK_INT16(tmp, pos, srcmbh->protid);
+	PACK_INT16(tmp, pos, srcmbh->length);
+	PACK_INT8(pos, srcmbh->uid);
+	PACK_INT8(pos, srcmbh->fc);
+	PACK_INT16(tmp, pos, srcmbh->offset);
+	PACK_INT16(tmp, pos, srcmbh->number);
+
+	return pos;
+}
+
+
+/*
+ * unpacks the buffer into the header
+ * returns NULL on error or points to end of data
+ */
+char * modbustcp_unpkt_header (modbustcp_header *destmbh, char *srcbuffer, int bufsize) {
+	uint16_t tmp;
+
+	// source memory valid
+	if (srcbuffer == NULL) {
+		errno = EFAULT;
+		return NULL;
+	}
+	if (bufsize < 12) {
+		errno = EOVERFLOW;
+		return NULL;
+	}
+
+	char *src = srcbuffer;
+
+	UNPACK_INT16(tmp, destmbh->transid, src);
+	UNPACK_INT16(tmp, destmbh->protid, src);
+	UNPACK_INT16(tmp, destmbh->length, src);
+	UNPACK_INT8(destmbh->uid, src);
+	UNPACK_INT8(destmbh->fc, src);
+	UNPACK_INT16(tmp, destmbh->offset, src);
+	UNPACK_INT16(tmp, destmbh->number, src);
+
+	return src;
+}
diff --git a/modbus.h b/modbus.h
new file mode 100644
index 0000000..2b598f1
--- /dev/null
+++ b/modbus.h
@@ -0,0 +1,33 @@
+/////////////////////////////////////////////////////////////////////////////////
+//
+// modbus.h is part of TestModbus-Client.
+//
+/////////////////////////////////////////////////////////////////////////////////
+
+#ifndef _MODBUS_H_
+#define _MODBUS_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <arpa/inet.h>
+
+/*
+ * this file will only contain the encoding and decoding functions
+ */
+
+struct {
+	uint16_t transid;	// transaction id
+	uint16_t protid;	// protocol id
+	uint16_t length;	// number of bytes followed
+	uint8_t uid;		// unit/slave id
+	uint8_t fc;			// function code
+	uint16_t offset;	// first register to read
+	uint16_t number;	// number of registers to read
+} typedef modbustcp_header;
+
+
+char * modbustcp_pkt_header (char *destbuffer, int bufsize, modbustcp_header *srcmbh);
+char * modbustcp_unpkt_header (modbustcp_header *destmbh, char *srcbuffer, int bufsize);
+
+
+#endif
diff --git a/nwthread.cc b/nwthread.cc
index ac25229..c535392 100644
--- a/nwthread.cc
+++ b/nwthread.cc
@@ -36,6 +36,11 @@ NetworkThread::NetworkThread() {
 	state = 0;
 	host = "";
 	port = "";
+	req_fc = -1;
+	req_offset = 0;
+	req_size = 0;
+	memset (&req_time, 0x0, sizeof (req_time));
+	req_timeout = 0;
 };
 
 NetworkThread::~NetworkThread() {
diff --git a/testmodbus-client.ui b/testmodbus-client.ui
index 54a4ec2..51bbcd7 100644
--- a/testmodbus-client.ui
+++ b/testmodbus-client.ui
@@ -2,6 +2,12 @@
 <!-- Generated with glade 3.40.0 -->
 <interface>
   <requires lib="gtk+" version="3.24"/>
+  <object class="GtkEntryBuffer" id="entrybuffer_numbers">
+    <property name="text" translatable="yes">16</property>
+  </object>
+  <object class="GtkEntryBuffer" id="entrybuffer_offset">
+    <property name="text" translatable="yes">0</property>
+  </object>
   <object class="GtkWindow" id="testmodbus-client">
     <property name="can-focus">False</property>
     <signal name="destroy" handler="gtk_main_quit" swapped="no"/>
@@ -355,6 +361,7 @@
                             <property name="receives-default">False</property>
                             <property name="active">True</property>
                             <property name="draw-indicator">True</property>
+                            <property name="group">cli_FC1</property>
                           </object>
                           <packing>
                             <property name="expand">False</property>
@@ -371,6 +378,7 @@
                             <property name="receives-default">False</property>
                             <property name="active">True</property>
                             <property name="draw-indicator">True</property>
+                            <property name="group">cli_FC1</property>
                           </object>
                           <packing>
                             <property name="expand">False</property>
@@ -387,6 +395,7 @@
                             <property name="receives-default">False</property>
                             <property name="active">True</property>
                             <property name="draw-indicator">True</property>
+                            <property name="group">cli_FC1</property>
                           </object>
                           <packing>
                             <property name="expand">False</property>
@@ -455,8 +464,10 @@
                           <object class="GtkEntry">
                             <property name="visible">True</property>
                             <property name="can-focus">True</property>
+                            <property name="buffer">entrybuffer_offset</property>
                             <property name="max-length">5</property>
                             <property name="width-chars">5</property>
+                            <property name="placeholder-text" translatable="yes">0</property>
                           </object>
                           <packing>
                             <property name="left-attach">1</property>
@@ -467,8 +478,10 @@
                           <object class="GtkEntry">
                             <property name="visible">True</property>
                             <property name="can-focus">True</property>
+                            <property name="buffer">entrybuffer_numbers</property>
                             <property name="max-length">5</property>
                             <property name="width-chars">5</property>
+                            <property name="placeholder-text" translatable="yes">16</property>
                           </object>
                           <packing>
                             <property name="left-attach">1</property>