diff --git a/c/include/dynamixel_sdk/packet_handler.h b/c/include/dynamixel_sdk/packet_handler.h
index 66bb29e2..287dd460 100644
--- a/c/include/dynamixel_sdk/packet_handler.h
+++ b/c/include/dynamixel_sdk/packet_handler.h
@@ -79,8 +79,6 @@ typedef struct
   uint8_t     *broadcast_ping_id_list;
 }PacketData;
 
-PacketData *packetData;
-
 WINDECLSPEC void        packetHandler       ();
 
 WINDECLSPEC const char *getTxRxResult       (int protocol_version, int result);
diff --git a/c/include/dynamixel_sdk/port_handler.h b/c/include/dynamixel_sdk/port_handler.h
index 77462484..5186dfac 100644
--- a/c/include/dynamixel_sdk/port_handler.h
+++ b/c/include/dynamixel_sdk/port_handler.h
@@ -42,11 +42,6 @@
 
 #include "robotis_def.h"
 
-static const int DEFAULT_BAUDRATE = 57600;
-
-int     g_used_port_num;
-uint8_t    *g_is_using;
-
 WINDECLSPEC int     portHandler             (const char *port_name);
 
 WINDECLSPEC uint8_t openPort                (int port_num);
diff --git a/c/src/dynamixel_sdk/group_bulk_read.c b/c/src/dynamixel_sdk/group_bulk_read.c
index 900e0b94..48f926c8 100644
--- a/c/src/dynamixel_sdk/group_bulk_read.c
+++ b/c/src/dynamixel_sdk/group_bulk_read.c
@@ -28,6 +28,8 @@
 #include "group_bulk_read.h"
 #endif
 
+extern PacketData *packetData;  // defined in packet_handler.c
+
 typedef struct
 {
   uint8_t     id;
diff --git a/c/src/dynamixel_sdk/group_bulk_write.c b/c/src/dynamixel_sdk/group_bulk_write.c
index d602cc85..eac1c034 100644
--- a/c/src/dynamixel_sdk/group_bulk_write.c
+++ b/c/src/dynamixel_sdk/group_bulk_write.c
@@ -27,6 +27,8 @@
 #include "group_bulk_write.h"
 #endif
 
+extern PacketData *packetData;  // defined in packet_handler.c
+
 typedef struct
 {
   uint8_t     id;
diff --git a/c/src/dynamixel_sdk/group_sync_read.c b/c/src/dynamixel_sdk/group_sync_read.c
index 9b0dbc3c..feb16c61 100644
--- a/c/src/dynamixel_sdk/group_sync_read.c
+++ b/c/src/dynamixel_sdk/group_sync_read.c
@@ -27,6 +27,8 @@
 #include "group_sync_read.h"
 #endif
 
+extern PacketData *packetData;  // defined in packet_handler.c
+
 typedef struct
 {
   uint8_t     id;
diff --git a/c/src/dynamixel_sdk/group_sync_write.c b/c/src/dynamixel_sdk/group_sync_write.c
index df7cfa62..26cc1522 100644
--- a/c/src/dynamixel_sdk/group_sync_write.c
+++ b/c/src/dynamixel_sdk/group_sync_write.c
@@ -27,6 +27,8 @@
 #include "group_sync_write.h"
 #endif
 
+extern PacketData *packetData;  // defined in packet_handler.c
+
 typedef struct
 {
   uint8_t     id;
diff --git a/c/src/dynamixel_sdk/packet_handler.c b/c/src/dynamixel_sdk/packet_handler.c
index fe4c0083..49de9395 100644
--- a/c/src/dynamixel_sdk/packet_handler.c
+++ b/c/src/dynamixel_sdk/packet_handler.c
@@ -33,6 +33,9 @@
 #include "protocol2_packet_handler.h"
 #endif
 
+PacketData *packetData;
+extern int g_used_port_num; // defined in port_handler.c
+
 void packetHandler()
 {
   int port_num;
diff --git a/c/src/dynamixel_sdk/port_handler.c b/c/src/dynamixel_sdk/port_handler.c
index 7f46ade2..45c39861 100644
--- a/c/src/dynamixel_sdk/port_handler.c
+++ b/c/src/dynamixel_sdk/port_handler.c
@@ -91,3 +91,8 @@ void    setPacketTimeoutMSec(int port_num, double msec) { setPacketTimeoutMSecWi
 uint8_t isPacketTimeout     (int port_num) { return isPacketTimeoutWindows(port_num); }
 
 #endif
+
+static const int DEFAULT_BAUDRATE = 57600;
+
+int g_used_port_num;
+uint8_t *g_is_using;
diff --git a/c/src/dynamixel_sdk/port_handler_linux.c b/c/src/dynamixel_sdk/port_handler_linux.c
index 965e64d1..4997eb31 100644
--- a/c/src/dynamixel_sdk/port_handler_linux.c
+++ b/c/src/dynamixel_sdk/port_handler_linux.c
@@ -89,6 +89,9 @@ typedef struct
 }PortData;
 
 static PortData *portData;
+extern int DEFAULT_BAUDRATE; // defined in port_handler.c
+extern int g_used_port_num; // defined in port_handler.c
+extern uint8_t *g_is_using; // defined in port_handler.c
 
 int portHandlerLinux(const char *port_name)
 {
diff --git a/c/src/dynamixel_sdk/port_handler_mac.c b/c/src/dynamixel_sdk/port_handler_mac.c
index 458dd4f7..cc22d653 100644
--- a/c/src/dynamixel_sdk/port_handler_mac.c
+++ b/c/src/dynamixel_sdk/port_handler_mac.c
@@ -56,6 +56,9 @@ typedef struct
 }PortData;
 
 static PortData *portData;
+extern int DEFAULT_BAUDRATE;  // defined in port_handler.c
+extern int g_used_port_num;   // defined in port_handler.c
+extern uint8_t *g_is_using;   // defined in port_handler.c
 
 int portHandlerMac(const char *port_name)
 {
diff --git a/c/src/dynamixel_sdk/port_handler_windows.c b/c/src/dynamixel_sdk/port_handler_windows.c
index e8d52adc..700a9f94 100644
--- a/c/src/dynamixel_sdk/port_handler_windows.c
+++ b/c/src/dynamixel_sdk/port_handler_windows.c
@@ -48,6 +48,9 @@ typedef struct
 }PortData;
 
 static PortData *portData;
+extern int DEFAULT_BAUDRATE;  // defined in port_handler.c
+extern int g_used_port_num;   // defined in port_handler.c
+extern uint8_t *g_is_using;   // defined in port_handler.c
 
 int portHandlerWindows(const char *port_name)
 {
diff --git a/c/src/dynamixel_sdk/protocol1_packet_handler.c b/c/src/dynamixel_sdk/protocol1_packet_handler.c
index 5e1eee76..74c89bee 100644
--- a/c/src/dynamixel_sdk/protocol1_packet_handler.c
+++ b/c/src/dynamixel_sdk/protocol1_packet_handler.c
@@ -49,6 +49,9 @@
 #define ERRBIT_OVERLOAD         32      // The current load cannot be controlled by the set torque.
 #define ERRBIT_INSTRUCTION      64      // Undefined instruction or delivering the action command without the reg_write command.
 
+extern PacketData *packetData;  // defined in packet_handler.c
+extern uint8_t *g_is_using;    // defined in port_handler.c
+
 const char *getTxRxResult1(int result)
 {
   switch (result)
@@ -701,7 +704,7 @@ void regWriteTxOnly1(int port_num, uint8_t id, uint16_t address, uint16_t length
   }
 
   txPacket1(port_num);
-  
+
   g_is_using[port_num] = False;
 }
 
diff --git a/c/src/dynamixel_sdk/protocol2_packet_handler.c b/c/src/dynamixel_sdk/protocol2_packet_handler.c
index 3f403482..1387db44 100644
--- a/c/src/dynamixel_sdk/protocol2_packet_handler.c
+++ b/c/src/dynamixel_sdk/protocol2_packet_handler.c
@@ -58,6 +58,9 @@
 
 #define ERRBIT_ALERT            128     //When the device has a problem, this bit is set to 1. Check "Device Status Check" value.
 
+extern PacketData *packetData;  // defined in packet_handler.c
+extern uint8_t *g_is_using;     // defined in port_handler.c
+
 const char *getTxRxResult2(int result)
 {
   switch (result)
@@ -251,13 +254,13 @@ void addStuffing(uint8_t *packet)
   uint16_t i;
   uint16_t packet_length_before_crc;
   uint16_t out_index, in_index;
-  
+
   int packet_length_in = DXL_MAKEWORD(packet[PKT_LENGTH_L], packet[PKT_LENGTH_H]);
   int packet_length_out = packet_length_in;
-  
+
   if (packet_length_in < 8) // INSTRUCTION, ADDR_L, ADDR_H, CRC16_L, CRC16_H + FF FF FD
     return;
-  
+
   packet_length_before_crc = packet_length_in - 2;
   for (i = 3; i < packet_length_before_crc; i++)
   {
@@ -265,10 +268,10 @@ void addStuffing(uint8_t *packet)
     if (packet_ptr[0] == 0xFF && packet_ptr[1] == 0xFF && packet_ptr[2] == 0xFD)
       packet_length_out++;
   }
-  
+
   if (packet_length_in == packet_length_out)  // no stuffing required
     return;
-  
+
   out_index  = packet_length_out + 6 - 2;  // last index before crc
   in_index   = packet_length_in + 6 - 2;   // last index before crc
   while (out_index != in_index)
@@ -548,7 +551,7 @@ uint16_t pingGetModelNum2(int port_num, uint8_t id)
     printf("[PingGetModeNum] memory allocation failed.. \n");
     return COMM_TX_FAIL;
   }
-  
+
   if (id >= BROADCAST_ID)
   {
     packetData[port_num].communication_result = COMM_NOT_AVAILABLE;
@@ -749,7 +752,7 @@ void clearMultiTurn2(int port_num, uint8_t id)
     printf("[ClearMultiTurn] memory allocation failed..\n");
     return;
   }
-  
+
   packetData[port_num].tx_packet[PKT_ID] = id;
   packetData[port_num].tx_packet[PKT_LENGTH_L] = 8;
   packetData[port_num].tx_packet[PKT_LENGTH_H] = 0;
@@ -772,7 +775,7 @@ void factoryReset2(int port_num, uint8_t id, uint8_t option)
     printf("[FactoryReset] memory allocation failed..\n");
     return;
   }
-  
+
   packetData[port_num].tx_packet[PKT_ID] = id;
   packetData[port_num].tx_packet[PKT_LENGTH_L] = 4;
   packetData[port_num].tx_packet[PKT_LENGTH_H] = 0;
@@ -792,7 +795,7 @@ void readTx2(int port_num, uint8_t id, uint16_t address, uint16_t length)
     printf("[ReadTx] memory allocation failed..\n");
     return;
   }
-  
+
   if (id >= BROADCAST_ID)
   {
     packetData[port_num].communication_result = COMM_NOT_AVAILABLE;
@@ -828,7 +831,7 @@ void readRx2(int port_num, uint16_t length)
     printf("[ReadRx] memory allocation failed..\n");
     return;
   }
-  
+
   rxPacket2(port_num);
   if (packetData[port_num].communication_result == COMM_SUCCESS)
   {
@@ -854,7 +857,7 @@ void readTxRx2(int port_num, uint8_t id, uint16_t address, uint16_t length)
     printf("[ReadTxRx] memory allocation failed..\n");
     return;
   }
-  
+
   if (id >= BROADCAST_ID)
   {
     packetData[port_num].communication_result = COMM_NOT_AVAILABLE;
@@ -1032,7 +1035,7 @@ void writeTxRx2(int port_num, uint8_t id, uint16_t address, uint16_t length)
     printf("[WriteTxRx] memory allocation failed..\n");
     return;
   }
-  
+
   packetData[port_num].tx_packet[PKT_ID] = id;
   packetData[port_num].tx_packet[PKT_LENGTH_L] = DXL_LOBYTE(length + 5);
   packetData[port_num].tx_packet[PKT_LENGTH_H] = DXL_HIBYTE(length + 5);