20120315

程式設計工藝大師














TCP   與   UDP  差異

熟悉網路的人，應該都聽過TCP與UDP，這裡我們簡單來
看看到底這兩個協定差別在那？

TCP(Transmission Control Protocol)
UDP(User Datagram Protocol)

TCP這個協定最主要的特色在於傳輸資料時，需要驗證資
料，確保正確性。所以花的時間稍多一點。

而UDP這個協定最主要的特色在於傳輸資料時，不需要驗
證資料，不保證正確性，所以比較省時間。而一般來說，
像是多媒體串流(streaming)就是使用這種協定。 

參考資料：http://hazuki016.pixnet.net/blog/post/13288265-tcp%E8%88%87udp%E7%9A%84%E6%AF%94%E8%BC%83














連線實習


如何做-


按電腦圖示

改右邊的屬性

server如同上步驟，LocalPort與remoteport相反

Client    to    server

Private Sub cmdConnect_Click()

  Winsock1.LocalPort = "6666"   '以便自動產生Local Port

  Winsock1.Connect "192.168.15.31"  '設定改成您 Server 電腦的IP 號碼

End Sub

Private Sub cmdExit_Click()

  Winsock1.SendData "close"

  DoEvents

  Winsock1.Close

  Winsock1.LocalPort = 0

End Sub

Private Sub cmdSend_Click()

  Winsock1.SendData txtOutput.Text

  DoEvents

End Sub

Private Sub Form_Load()

  Winsock1.RemotePort = 7777  '設定與Server端做Listen的Port相同

End Sub

Private Sub Form_Unload(Cancel As Integer)

If Winsock1.State <> sckClosed Then

   cmdExit_Click

End If

End Sub

Private Sub Winsock1_Connect()

If Winsock1.State = sckConnected Then

   lstInput.AddItem "Connected! LocalPort =" & Winsock1.LocalPort _

                    & " RemptePort = " & Winsock1.RemotePort

End If

End Sub

Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)

  Dim mydata As String

  Winsock1.GetData mydata, vbString

  lstInput.AddItem mydata

End Sub

Private Sub Winsock1_Error(ByVal Number As Integer, Description As String, ByVal Scode As Long, ByVal Source As String, ByVal HelpFile As String, ByVal HelpContext As Long, CancelDisplay As Boolean)

  lstInput.AddItem Description

End Sub

server   to   Client

Option Explicit

Private Sub cmdSend_Click()

  Winsock1.SendData txtSend.Text

End Sub

Private Sub Form_Load()

  Winsock1.LocalPort = 7777

  Winsock1.Listen  '監聽

End Sub

Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)

  Dim strData As String

  Winsock1.GetData strData, vbString

  txtReceived.Text = strData

  If strData = "close" Then

    Winsock1.Close

    cmdSend.Enabled = False

    Winsock1.Listen

  End If

End Sub

Private Sub Winsock1_ConnectionRequest(ByVal requestID As Long)

MsgBox "有人敲門"

  Winsock1.Close

  Winsock1.Accept requestID  '改成接受

  cmdSend.Enabled = True

End Sub