I have been trying my hand at handling packets and bytes for the first time, and I have not been able to obtain the packet length correctly so far after many different techniques.
Code:
Public Shared Sub Client(packet As Packet)
Console.WriteLine( _
"Client -> " & _
packet.Timestamp.ToString("yyyy-MM-dd hh:mm:ss.fff") & _
" length:" & Convert.ToString(packet.Length))
'Define Byte Array
Dim clientPacket As Byte() = packet.Buffer
' Open a Binary Reader
Dim memStream As MemoryStream = New MemoryStream(clientPacket)
Dim bReader As BinaryReader = New BinaryReader(memStream)
' Remove the Ethernet Header
Dim ethBytes As Byte() = bReader.ReadBytes(14)
' Remove the IPv4 Header
Dim IPv4Bytes As Byte() = bReader.ReadBytes(20)
' Remove the TCP Header
Dim TCPBytes As Byte() = bReader.ReadBytes(20)
' Get the packet length
If clientPacket.Length > 54 Then
Dim len As UInt32 = bReader.ReadUInt32
Console.WriteLine(len)
End If
End Sub
So far, all of my attempts at having the console write the data length have resulted in failure. I validated the endianness and actually wrote out the bytes to verify that I was handling the correct data.
Example bytes:
00 00 00 24 -> UINT32 is 36 bytes, but I am getting an array of Integers like 3808493568
How can I fix this?
I agree with Hans, endianness is your problem. Also, I'd recommend you use the BitConverter class on the clientPacket array, easier than using streams.
Dim len As UInt32
Dim arr() As Byte
arr = {0, 0, 0, 24}
len = BitConverter.ToUInt32(arr, 0)
Console.Write(len.ToString) 'returns 402653184
arr = {24, 0, 0, 0}
len = BitConverter.ToUInt32(arr, 0)
Console.Write(len.ToString) 'returns 24
For your code, I think this might work (untested):
If clientPacket.Length > 54 Then
Dim lenBytes As Byte() = bReader.ReadBytes(4)
Array.Reverse(lenBytes, 0, 4)
Dim len As UInt32 = BitConverter.ToUInt32(lenBytes, 0)
Related
For some time I've been working on learning how to program VB.NET. With the help of this page and the internet, I managed to create a program that sends some hex values to an interface box and get a routine response from it.
The problem here is that the communication was TCP/IP. But now I have a new box with a USB interface and now I do not have the slightest idea of how to send and receive those same hex values using the Serial port.
Below is the code. I don't know if someone could help me set it up for a serial port named COM13 or at least explain to me what to do.
This is what the program does.
Push scan
Connects to the TCP/IP of the BOX (10.2.12.65)
Sends the activation protocol E1 33
Sends the get date command 05 6c 29 f1 3c 81
Box responds back date with bytes
When the program reads the byte corresponding to 81(hex) it starts converting them into characters and adding them to a string to be displayed on the textbox on the bottom.
That's basically it. The problem is that until now I have been able to send only text strings but the box does not recognize it and it responds garbage and not the date.
Here is the code:
Imports System.Net.Sockets
Imports System.Threading
Imports System.IO
Public Class Form1
Dim client As New TcpClient
Dim transmit As NetworkStream
Dim protocol As Byte()
Dim data As Byte()
Dim ByteArrayToHexStr As String = String.Empty
Dim message As String
Dim datos_byte As Byte()
Dim respuesta As [String] = [String].Empty
Dim transision As [String] = [String].Empty
Dim Date_full As [String] = [String].Empty
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
TextBox1.Clear()
client = New TcpClient("10.2.12.65", 10001)
transmit = client.GetStream()
protocol = {225, 51} ' E1 33 in hex value
transmit.Write(protocol, 0, protocol.Length)
Thread.Sleep(45)
data = {5, 108, 41, 241, 60, 129} ' 05 6c 29 f1 3c 81 in hex value
transmit.Write(data, 0, data.Length)
data = New Byte(66) {}
Thread.Sleep(45)
Dim bytes As Int32 = transmit.Read(data, 0, data.Length)
Dim Date1 As String = String.Empty
Dim Date2 As String = String.Empty
Dim Date_temp As Integer = 0
For i As Integer = 0 To UBound(data)
Date1 = data(i)
If Date1 = "129" Then
Date_temp = i + 1
i = 1000
For k As Integer = 0 To 5
If k = 0 Then
Date1 = data(Date_temp + k)
Date_full = Chr(Date1)
Else
Date1 = data(Date_temp + k)
Date2 = Chr(Date1)
Date_full = Date_full & Date2
End If
Next
Else
End If
Next
Thread.Sleep(45)
transmit.Close()
client.Close()
TextBox1.Text = TextBox1.Text & Date_full
End Sub
End Class
Please have a look at Microsoft's example of the SerialPort class: https://msdn.microsoft.com/en-us/library/system.io.ports.serialport(v=vs.110).aspx?cs-save-lang=1&cs-lang=vb#code-snippet-2
If you get garbage back that might indicate the baudrate is configured incorrectly. I'm not sure what you mean by 'box' but this device should have a specified baudrate which you should be able to find in its datasheet or product information.
I have the following functions to generate md5-hashes for files. The functions work great for small files, but crashes and generate Run-time error 7 - Out of memory when I try to hash files over ~250 MB (I don't actually know at which exact size it breaks, but files below 200 MB work fine).
I don't understand why it breaks at a certain size, so if anyone could shed some light on that I would appreciate it a lot.
Also, is there anything I can do to make the functions handle larger files? I intend to use the functions in a larger tool where I will need to generate hashes for files of unknown sizes. Most will be small enough for the current functions to work, but I will have to be able to handle large files as well.
I got my current functions from the most upvoted answer this post How to get the MD5 hex hash for a file using VBA?
Public Function FileToMD5Hex(ByVal strFileName As String) As String
Dim varEnc As Variant
Dim varBytes As Variant
Dim strOut As String
Dim intPos As Integer
Set varEnc = CreateObject("System.Security.Cryptography.MD5CryptoServiceProvider")
'Convert the string to a byte array and hash it
varBytes = GetFileBytes(strFileName)
varBytes = varEnc.ComputeHash_2((varBytes))
'Convert the byte array to a hex string
For intPos = 1 To LenB(varBytes)
strOut = strOut & LCase(Right("0" & Hex(AscB(MidB(varBytes, intPos, 1))), 2))
Next
FileToMD5Hex = strOut
Set varEnc = Nothing
End Function
Private Function GetFileBytes(ByVal strPath As String) As Byte()
Dim lngFileNum As Long
Dim bytRtnVal() As Byte
lngFileNum = FreeFile
'If file exists, get number of bytes
If LenB(Dir(strPath)) Then
Open strPath For Binary Access Read As lngFileNum
ReDim bytRtnVal(LOF(lngFileNum)) As Byte
Get lngFileNum, , bytRtnVal
Close lngFileNum
Else
MsgBox "Filen finns inte" & vbCrLf & "Avbryter", vbCritical, "Filen hittades inte"
Exit Function
End If
GetFileBytes = bytRtnVal
Erase bytRtnVal
End Function
Thank you
It looks like you reached the memory limit.
A better way would be to compute the MD5 of the file by block:
Public Function ComputeMD5(filepath As String) As String
Dim buffer() As Byte, svc As Object, hFile%, blockSize&, i&
blockSize = 2 ^ 16
' open the file '
If Len(Dir(filepath)) Then Else Err.Raise 5, , "file not found" & vbCr & filepath
hFile = FreeFile
Open filepath For Binary Access Read As hFile
' allocate buffer '
If LOF(hFile) < blockSize Then blockSize = ((LOF(hFile) + 1024) \ 1024) * 1024
ReDim buffer(0 To blockSize - 1)
' compute hash '
Set svc = CreateObject("System.Security.Cryptography.MD5CryptoServiceProvider")
For i = 1 To LOF(hFile) \ blockSize
Get hFile, , buffer
svc.TransformBlock buffer, 0, blockSize, buffer, 0
Next
Get hFile, , buffer
svc.TransformFinalBlock buffer, 0, LOF(hFile) Mod blockSize
buffer = svc.Hash
' cleanup '
svc.Clear
Close hFile
' convert to an hexa string '
ComputeMD5 = String$(32, "0")
For i = 0 To 15
Mid$(ComputeMD5, i + i + 2 + (buffer(i) > 15)) = Hex(buffer(i))
Next
End Function
This is an extension to FlorentB's answer, which worked brilliantly for me until my files surpassed the 2GB LOF() size limit.
I tried to adapt for getting file length by alternate means as follows:
Public Function ComputeMD5(filepath As String) As String
If Len(Dir(filepath)) Then Else Err.Raise 5, , "File not found." & vbCr & filepath
Dim blockSize As Long: blockSize = 2 ^ 20
Dim blockSize_f As Double
Dim buffer() As Byte
Dim fileLength As Variant
Dim hFile As Integer
Dim n_Reads As Long
Dim i As Long
Dim svc As Object: Set svc = CreateObject("System.Security.Cryptography.MD5CryptoServiceProvider")
fileLength = DecGetFileSize(filepath)
If fileLength < blockSize Then blockSize = ((fileLength + 1024) \ 1024) * 1024
ReDim buffer(0 To blockSize - 1)
n_Reads = fileLength / blockSize
blockSize_f = fileLength - (CDbl(blockSize) * n_Reads)
hFile = FreeFile
Open filepath For Binary Access Read As hFile
For i = 1 To n_Reads
Get hFile, i, buffer
svc.TransformBlock buffer, 0, blockSize, buffer, 0
Next i
Get hFile, i, buffer
svc.TransformFinalBlock buffer, 0, blockSize_f
buffer = svc.Hash
svc.Clear
Close hFile
ComputeMD5 = String$(32, "0")
For i = 0 To 15
Mid$(ComputeMD5, i + i + 2 + (buffer(i) > 15)) = Hex(buffer(i))
Next
End Function
Public Function DecGetFileSize(fname As String) As Variant
Dim fso As New FileSystemObject
Dim f: Set f = fso.GetFile(fname)
DecGetFileSize = CDec(f.Size)
Set f = Nothing
Set fso = Nothing
End Function
This all runs fine, returning a string, however that string does not equal the MD5 calculated using other tools on the same file.
I can't work out where the discrepancy is originating.
I've checked and double checked filelength, n_reads, blockSize and blockSize_f and I'm sure those values are all correct.
I had some trouble with the Get function, where if I didn't explicitly tell it the block number, it dies at block 2048.
Any ideas / pointers would be much appreciated.
I'm trying to figure out how to read a section of bytes (Say 16) starting at a specific address, say 0x2050. I'd like to get the 16 bits output in hex values into a label.
I've been trying to figure out BinaryReader, and FileStreams but I'm not entirely sure what the difference is, or which one I should be using.
*I've seen a lot of threads mentioning file size could be an issue, and I'd like to point out that some files I'll be checking may be up to 4gb in size.
I've tried the following:
Dim bytes() As Byte = New Byte(OpenedFile.Length) {}
ListBox1.Items.Add(Conversion.Hex(OpenedFile.Read(bytes, &H2050, 6)))
But this simply writes 6 bytes to the file, and I'm not sure why. There is no output in the listbox.
How about something like the following?:
Sub Main()
Dim pos As Long = 8272
Dim requiredBytes As Integer = 2
Dim value(0 To requiredBytes - 1) As Byte
Using reader As New BinaryReader(File.Open("File.bin", FileMode.Open))
' Loop through length of file.
Dim fileLength As Long = reader.BaseStream.Length
Dim byteCount As Integer = 0
reader.BaseStream.Seek(pos, SeekOrigin.Begin)
While pos < fileLength And byteCount < requiredBytes
value(byteCount) = reader.ReadByte()
pos += 1
byteCount += 1
End While
End Using
Dim displayValue As String
displayValue = BitConverter.ToString(value)
End Sub
I need a way to read from a FileStream every single char. Char by Char.
Every time I read a char, I need to increment the FileStream.Position.
I am trying the code snippet, but it returns more than one char:
Dim bytes(1) As Byte
Dim nBytes As Integer = oFile.Read(bytes, 0, bytes.Length)
Dim nChars As Integer = decoder8.GetCharCount(bytes, 0, nBytes)
Dim chars(nChars - 1) As Char
nChars = decoder8.GetChars(bytes, 0, nBytes, chars, 0)
Return New String(chars, 0, nChars)
You could use a StreamReader and it's Read method instead, couldn't you?
Using rd = New StreamReader("path", Encoding.UTF8)
While rd.Peek() >= 0
Dim c As Char = Chr(rd.Read())
Console.WriteLine("Next character: " & c)
End While
End Using
StreamReader.Read
Reads the next character from the input stream and advances the
character position by one character.
Assuming that oFile is of type FileStream then
Dim nBytes As Integer = oFile.ReadByte()
should work.
How can I get the MD5 hex hash for a file using VBA?
I need a version that works for a file.
Something as simple as this Python code:
import hashlib
def md5_for_file(fileLocation, block_size=2**20):
f = open(fileLocation)
md5 = hashlib.md5()
while True:
data = f.read(block_size)
if not data:
break
md5.update(data)
f.close()
return md5.hexdigest()
But in VBA.
An older question that could use a better answer. These functions are specifically for hashing files, not for hashing passwords. As a bonus, I'm including a function for SHA1. If you get rid of the type declarations these functions work in VBScript too except that the GetFileBytes function needs to be changed to use FileSystemObject (or possibly ADO Stream) as the Free File doesn't exist in VBScript.
Private Sub TestMD5()
Debug.Print FileToMD5Hex("C:\test.txt")
Debug.Print FileToSHA1Hex("C:\test.txt")
End Sub
Public Function FileToMD5Hex(sFileName As String) As String
Dim enc
Dim bytes
Dim outstr As String
Dim pos As Integer
Set enc = CreateObject("System.Security.Cryptography.MD5CryptoServiceProvider")
'Convert the string to a byte array and hash it
bytes = GetFileBytes(sFileName)
bytes = enc.ComputeHash_2((bytes))
'Convert the byte array to a hex string
For pos = 1 To LenB(bytes)
outstr = outstr & LCase(Right("0" & Hex(AscB(MidB(bytes, pos, 1))), 2))
Next
FileToMD5Hex = outstr
Set enc = Nothing
End Function
Public Function FileToSHA1Hex(sFileName As String) As String
Dim enc
Dim bytes
Dim outstr As String
Dim pos As Integer
Set enc = CreateObject("System.Security.Cryptography.SHA1CryptoServiceProvider")
'Convert the string to a byte array and hash it
bytes = GetFileBytes(sFileName)
bytes = enc.ComputeHash_2((bytes))
'Convert the byte array to a hex string
For pos = 1 To LenB(bytes)
outstr = outstr & LCase(Right("0" & Hex(AscB(MidB(bytes, pos, 1))), 2))
Next
FileToSHA1Hex = outstr 'Returns a 40 byte/character hex string
Set enc = Nothing
End Function
Private Function GetFileBytes(ByVal path As String) As Byte()
Dim lngFileNum As Long
Dim bytRtnVal() As Byte
lngFileNum = FreeFile
If LenB(Dir(path)) Then ''// Does file exist?
Open path For Binary Access Read As lngFileNum
ReDim bytRtnVal(LOF(lngFileNum) - 1&) As Byte
Get lngFileNum, , bytRtnVal
Close lngFileNum
Else
Err.Raise 53
End If
GetFileBytes = bytRtnVal
Erase bytRtnVal
End Function
This should do it:
Dim fileBytes() As Byte = File.ReadAllBytes(path:=fullPath)
Dim Md5 As New MD5CryptoServiceProvider()
Dim byteHash() As Byte = Md5.ComputeHash(fileBytes)
Return Convert.ToBase64String(byteHash)