hi Guys,
i have several clients on a LAN network, these clients all have access to a particular sql server. i want to write an application that allows any client on the network to send one or more messages to another client on the network providing that both clients have access to the specified sql server.
i don't know what class or component i should read on, if anyone has information on how to achieve this i would be grateful.
Regards
I created a similar thing on a project once.
Here's what I did.
I created a class with two main methods. One for reading messages from the database, and one for writing the message to the database.
I then used threading to run that class and let it trigger the read method every 5 minutes (or so).
If a message was found, destined to a user running a certain instance of the client it displayed a MessageBox containing who sent it, when and the message.
Here is the class I created.
It was a while ago, so it may seem a bit ugly. (But it works, mostly.)
Imports System.Data.SqlClient
Imports System.Threading
Namespace Classes
Public Class clsIM
#Region " Member Variables "
Private strUser As String
Private strErr As String
Private isHidden As Boolean = False
Private con As SqlConnection
Private m_clsThread As Thread
Private m_clsSynchronizingObject As System.ComponentModel.ISynchronizeInvoke
Private m_clsNotifyDelegate As NotifyProgress
Public Delegate Sub NotifyProgress(ByVal Message As String)
#End Region
#Region " Constructors "
Public Sub New(ByVal UserName As String)
'The username of the current user
strUser = UserName
End Sub
Public Sub New(ByVal UserName As String, ByVal SynchronizingObject As System.ComponentModel.ISynchronizeInvoke, ByVal NotifyDelegate As NotifyProgress)
'The username of the current user
strUser = UserName
m_clsSynchronizingObject = SynchronizingObject
m_clsNotifyDelegate = NotifyDelegate
End Sub
#End Region
#Region " Public Methods "
Public Sub Start()
m_clsThread = New Thread(AddressOf PollMessages)
m_clsThread.Name = "Instant Messages"
m_clsThread.IsBackground = True
m_clsThread.Start()
End Sub
Public Function SendMessage(ByVal ToUser As String, ByVal DateTime As String, ByVal Message As String) As Boolean
Dim SQL As String = ""
Dim arrToUser() As String = Nothing
Dim i As Integer = 0
con = New SqlConnection(ConStr)
Dim com As SqlCommand
Dim dr As SqlDataReader
Try
If ToUser = "allUser" Then
con.Open()
com = New SqlCommand("SELECT username FROM WhoOnline", con)
dr = com.ExecuteReader(CommandBehavior.CloseConnection)
If dr.HasRows Then
While dr.Read
ReDim Preserve arrToUser(i)
If Not IsDBNull(dr.Item("username")) Then arrToUser(i) = dr.Item("username")
i += 1
End While
End If
con.Close()
con.Open()
For j As Integer = 0 To arrToUser.Length - 1
SQL = "INSERT INTO tblInstantMessage ([From],[To],Message,Sent) VALUES ('Admin','" & arrToUser(j) & "','" & Message & "','" & DateTime & "')"
com = New SqlCommand(SQL, con)
If com.ExecuteNonQuery = 0 Then
strErr = "Unable to send message to user: " & arrToUser(j) & ". Cancelling. Try again later."
con.Close()
Return False
End If
Next
con.Close()
Else
con.Open()
SQL = "INSERT INTO tblInstantMessage ([From],[To],Message,Sent) VALUES ('" & strUser & "','" & ToUser & "','" & Message & "','" & DateTime & "')"
com = New SqlCommand(SQL, con)
If com.ExecuteNonQuery = 0 Then
strErr = "Unable to send message. Try again later."
con.Close()
Return False
End If
con.Close()
End If
Catch ex As Exception
If con.State = ConnectionState.Open Then
con.Close()
End If
MessageBox.Show("An error occured while sending the message." & vbCrLf & "Error Message: " & ex.Message, "Database error", MessageBoxButtons.OK, MessageBoxIcon.Error)
Return False
End Try
Return True
End Function
Public Function SendMessage(ByVal ToUsers() As String, ByVal FromUser As String, ByVal DateTime As String, ByVal Message As String) As Boolean
Dim SQL As String = ""
Dim arrToUser() As String = Nothing
Dim i As Integer = 0
con = New SqlConnection(ConStr)
Dim com As SqlCommand
Dim dr As SqlDataReader
Try
con.Open()
com = New SqlCommand("SELECT username FROM WhoOnline", con)
dr = com.ExecuteReader(CommandBehavior.CloseConnection)
If dr.HasRows Then
While dr.Read
If Not IsDBNull(dr.Item("username")) AndAlso Array.IndexOf(ToUsers, dr.Item("username").ToString.ToUpper, 0) > -1 Then
ReDim Preserve arrToUser(i)
arrToUser(i) = dr.Item("username")
i += 1
End If
End While
End If
con.Close()
con.Open()
For j As Integer = 0 To arrToUser.Length - 1
SQL = "INSERT INTO tblInstantMessage ([From],[To],Message,Sent) VALUES ('" & FromUser & "','" & arrToUser(j) & "','" & Message & "','" & DateTime & "')"
com = New SqlCommand(SQL, con)
If com.ExecuteNonQuery = 0 Then
strErr = "Unable to send message to user: " & arrToUser(j) & ". Cancelling. Try again later."
con.Close()
Return False
End If
Next
con.Close()
Catch ex As Exception
If con.State = ConnectionState.Open Then
con.Close()
End If
MessageBox.Show("An error occured while sending the message." & vbCrLf & "Error Message: " & ex.Message, "Database error", MessageBoxButtons.OK, MessageBoxIcon.Error)
Return False
End Try
Return True
End Function
''' <summary>
''' Method for killing the thread
''' </summary>
''' <remarks></remarks>
Public Sub KillIM()
If m_clsThread.IsAlive = True Then
m_clsThread.Abort()
End If
If con.State = ConnectionState.Open Then
con.Close()
End If
End Sub
#End Region
#Region " Private Methods "
''' <summary>
''' Check for new messages
''' </summary>
''' <remarks></remarks>
Private Sub PollMessages()
While m_clsThread.ThreadState = ThreadState.Background
If Not m_clsThread.ThreadState = ThreadState.WaitSleepJoin Then
RetrieveMessage()
End If
End While
End Sub
''' <summary>
''' Fetch new messages
''' </summary>
''' <remarks></remarks>
Private Sub RetrieveMessage()
If strUser = "" Then Exit Sub
Dim strSent As String = ""
Dim dr As SqlDataReader
con = New SqlConnection(ConStr)
Try
con.Open()
Dim com As SqlCommand = New SqlCommand("SELECT [From],[To],Message,Sent FROM tblInstantMessage WHERE [To] = '" & strUser & "'", con)
dr = com.ExecuteReader(CommandBehavior.CloseConnection)
If dr.HasRows Then
While dr.Read
If Not IsDBNull(dr.Item("Message")) Then
NotifyUI(dr.Item("From") & "¤" & dr.Item("Message") & "¤" & dr.Item("Sent"))
End If
End While
If isHidden = False Then
RemoveMessages(strUser)
End If
End If
dr.Close()
Catch ex As Exception
End Try
Thread.Sleep(5000)
'm_clsThread.Sleep(5000)
End Sub
''' <summary>
''' Remove fetched messages
''' </summary>
''' <param name="ToUser">Recipient</param>
Private Sub RemoveMessages(ByVal ToUser As String)
Try
Dim con As SqlConnection = New SqlConnection(ConStr)
con.Open()
Dim com As SqlCommand = New SqlCommand("DELETE FROM tblInstantMessage WHERE [To] = '" & ToUser & "'", con)
com.ExecuteNonQuery()
con.Close()
Catch ex As Exception
End Try
End Sub
''' <summary>
''' Report back to main thread
''' </summary>
''' <param name="Message">Message to send to main thread</param>
Private Sub NotifyUI(ByVal Message As String)
If Not m_clsNotifyDelegate Is Nothing Then
Dim args(0) As Object
args(0) = Message
m_clsSynchronizingObject.Invoke(m_clsNotifyDelegate, args)
End If
End Sub
#End Region
#Region " Properties "
Public Property FormIsHidden() As Boolean
Get
Return isHidden
End Get
Set(ByVal value As Boolean)
isHidden = value
End Set
End Property
Public ReadOnly Property IsAlive() As Boolean
Get
If m_clsThread.IsAlive = True Then
Return True
Else
Return False
End If
End Get
End Property
#End Region
End Class
End NamespaceAnd here's how to use it.
On the main startup form, declare an instance of the class as Public and simply call the Start method.
Also add a method for displaying the message.
Public IM As clsIM
Private Sub Start_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
IM = New clsIM(userid, Me, New clsIM.NotifyProgress(AddressOf PrintProgress))
If IM IsNot Nothing Then
IM.FormIsHidden = False
IM.Start()
End If
End Sub
Private Sub PrintProgress(ByVal Message As String)
Dim strMessage() As String = Message.Split("¤")
Dim con As SqlConnection
Dim com As SqlCommand
Dim dr As SqlDataReader
If IM.FormIsHidden = False Then
MessageBox.Show("Sent: " & strMessage(2) & vbCrLf & vbCrLf & strMessage(1), "Message from: " & strMessage(0), MessageBoxButtons.OK, MessageBoxIcon.None)
End If
End SubAnd from whatever form you intend to send the message:
IM.SendMessage("to user", "date and time", "message")We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.