diff --git a/sources/DSS/.vscode/tasks.json b/sources/DSS/.vscode/tasks.json
index 105b8cb..9a48e77 100644
--- a/sources/DSS/.vscode/tasks.json
+++ b/sources/DSS/.vscode/tasks.json
@@ -166,7 +166,7 @@
             },
             "group": {
                 "kind": "build",
-                "isDefault": true
+                "isDefault": false
             }
         },
 
diff --git a/sources/DSS/tftp.asm b/sources/DSS/tftp.asm
index 0ccfa29..a7b87d7 100644
--- a/sources/DSS/tftp.asm
+++ b/sources/DSS/tftp.asm
@@ -8,19 +8,19 @@
 	MODULE TFTP
 
 ; ------------------------------------------------------
-; Operation codes 2b for tftp packet header
+; Operation codes 2b for tftp packet header  (bytes swapped)
 ; ------------------------------------------------------
 
 ; Opcode Read Request
-OP_RRQ		EQU '01'
+OP_RRQ		EQU '10'
 ; Opcode Write Request
-OP_WRQ		EQU	'02'
+OP_WRQ		EQU	'20'
 ; Opcode Data packet
-OP_DATA		EQU '03'
+OP_DATA		EQU '30'
 ; Opcode Acknowledge packet
-OP_ACK		EQU '04'
+OP_ACK		EQU '40'
 ; Opcode Error packet
-OP_ERROR	EQU '05'
+OP_ERROR	EQU '50'
 
 ; ------------------------------------------------------
 ; Build packet for request file from TFTF-server
@@ -30,7 +30,7 @@ BUILD_RRQ_PACKET
 	PUSH	DE
 	LD		DE,OP_RRQ									; opcode
 	CALL	.BUILD_RW_PACKET
-	POP		HL,DE
+	POP		DE
 	RET
 
 ; ------------------------------------------------------
@@ -40,15 +40,14 @@ BUILD_RRQ_PACKET
 	PUSH	DE
 	LD		DE,OP_WRQ									; opcode
 	CALL	.BUILD_RW_PACKET
-	POP		HL,DE
+	POP		DE
 	RET
 
 ; ------------------------------------------------------
 ; Build packet for write file or receive form TFTF-server
 ; ------------------------------------------------------
-.BUILD_RW_PACKET	
+.BUILD_RW_PACKET
 	LD		HL,TFTP_BUFF
-	PUSH	HL
 	LD		(HL), DE
 	INC		HL
 	INC		HL
@@ -65,14 +64,24 @@ BUILD_RRQ_PACKET
 	; Mode 'octet'Z
 .BRP_MOD
 	INC 	HL
-	LD		DE,'ct'
+	LD		DE,'co'
 	LD		(HL),DE
 	INC 	HL
+	INC 	HL
 	LD		DE,'et'
 	LD		(HL),DE
 	INC 	HL
+	INC 	HL
 	LD		DE,'t'
 	LD		(HL),DE
+	INC 	HL
+	INC 	HL
+	; Calculate packet length
+	LD		DE, TFTP_BUFF
+	SBC		HL,DE
+	EX		DE,HL
+	LD		HL,TFTF_PACKET_LEN
+	LD		(HL),DE
 	RET
 
 ; ------------------------------------------------------
@@ -157,6 +166,8 @@ CHK_ERROR
 	DB "Unknown TFTP packet received!"Z
 
 ; Buffer for UDP datagram with TFTP payload
+TFTF_PACKET_LEN
+	DW 0
 TFTP_BUFF
 	DS 516,0
 
diff --git a/sources/DSS/wtftp.asm b/sources/DSS/wtftp.asm
index 1be358a..fb0940a 100644
--- a/sources/DSS/wtftp.asm
+++ b/sources/DSS/wtftp.asm
@@ -8,7 +8,7 @@
 
 ; Set to 1 to turn debug ON with DeZog VSCode plugin
 ; Set to 0 to compile .EXE
-;	DEFINE			DEBUG
+	DEFINE			DEBUG
 
 ; Set to 1 to output TRACE messages
 	DEFINE 			TRACE
@@ -62,7 +62,7 @@ EXE_HEADER
 START
 	
     IFDEF DEBUG
-    	LD 		IX,CMD_LINE_TFTP_D1
+    	LD 		IX,CMD_LINE_TFTP_U
 		LD		SP, STACK_TOP		
     ENDIF
 	
@@ -121,6 +121,7 @@ OK_EXIT
 	JP		WCOMMON.EXIT
 
 ; ------------------------------------------------------
+; Parse command line parameters
 ; IX - points to cmd line
 ; ------------------------------------------------------
 PARSE_CMD_LINE
@@ -174,7 +175,6 @@ OUT_USAGE_MSG
 	PRINTLN	MSG_HLP
 	JP		OK_EXIT
 
-
 ; ------------------------------------------------------
 ; Move srv name and port number from (HL) to (DE)
 ; ------------------------------------------------------
@@ -237,8 +237,6 @@ GET_SRV_PARAMS
 .GDNF_NXT	
 	INC		HL
 	LD		A,(HL)
-;	OR		A
-;	JR		Z,.GDNF_END
 	CP		0x21
 	JP		M,.GDNF_END
 	LD		(DE),A
@@ -261,8 +259,8 @@ GET_SRV_PARAMS
 	RET
 
 ; ------------------------------------------------------
-; Get local file name from command string
-;
+; Get local file name from command line
+; Inp: HL -> command line
 ; ------------------------------------------------------
 GET_LFN
 	PUSH	BC,DE
@@ -342,7 +340,6 @@ OPEN_LOCAL_FILE
 	JR		NZ,.OLF_SKP_CP
 	
 	LD		HL, @TMP_BUFF
-	;PUSH	HL
 	CALL	UTIL.GET_CUR_DIR
 	LD		DE,LOC_FILE
 	LD		B,128
@@ -356,7 +353,6 @@ OPEN_LOCAL_FILE
 	DJNZ	.OLF_NXT	
 .OLF_EFN
 	LD		HL, @TMP_BUFF
-	;POP		HL
 
 	; HL - points to file path name
 .OLF_SKP_CP
@@ -432,8 +428,6 @@ CLOSE_LOCAL_FILE
 	CALL	DSS_ERROR.CHECK
 	RET
 
-
-
 ; ------------------------------------------------------
 ; Display current working mode
 ; ------------------------------------------------------