开发环境 VB.Net2005   Windows2003

'调用方式

If Logined() Then

MsgBox("登陆成功")

Else

MsgBox("登陆失败")

End If

'功能函数

Imports System

Imports System.Net

Imports System.IO

Imports System.Text

Imports System.Net.Sockets

Public Const BLOCK_SIZE = 512

Private Obj_ClientSocket As Socket

Private Str_Domain As String = "ftp.lob.cn"          'ftp服务器地址

Private Str_User As String = "lob"                       'ftp登陆帐号

Private Str_Password As String = "www.lob.cn"    'ftp登陆密码

Private Int_RemotePort As Integer = 21              'ftp服务器端口

Private Int_Reply, Int_Bytes As Int32

Private Str_Message, Str_Reply As String

Private Byte_Buffer(BLOCK_SIZE) As Byte

Private ASCII As Encoding = Encoding.ASCII

Public Function Logined() As Boolean  '乐博网www.lob.cn会员逍遥原创

Obj_ClientSocket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)

Dim x_lob As New IPEndPoint(Dns.GetHostEntry(Str_Domain).AddressList(0), Int_RemotePort)

Try

Obj_ClientSocket.Connect(x_lob)

Catch ex As Exception

MsgBox("无法登陆远程Ftp服务器")

End Try

Str_Message = ""

Str_Reply = ServerReply()

Int_Reply = Int32.Parse(Str_Reply.Substring(0, 3))

If (Int_Reply  220) Then

MsgBox(Str_Reply.Substring(4))

End If

SendCommand("USER " & Str_User)

Str_Reply = ServerReply(True)

Int_Reply = Int32.Parse(Str_Reply.Substring(0, 3))

If (Not (Int_Reply = 331 Or Int_Reply = 230)) Then

MsgBox(Str_Reply.Substring(4) )

Return False

End If

If (Int_Reply  230) Then

SendCommand("PASS " & Str_Password)

Str_Reply = ServerReply(True)

Int_Reply = Int32.Parse(Str_Reply.Substring(0, 3))

If (Not (Int_Reply = 230 Or Int_Reply = 202)) Then

MsgBox(Str_Reply.Substring(4))

Return False

End If

End If

Return True

End Function

Private Function ServerReply(Optional ByVal Bool_Clear As Boolean = False) As String

Dim Sep As Char = ControlChars.Lf

Dim Arr_Msg() As String

If (Bool_Clear) Then

Str_Message = ""

End If

Do While (True)

Array.Clear(Byte_Buffer, 0, BLOCK_SIZE)

Int_Bytes = Obj_ClientSocket.Receive(Byte_Buffer, Byte_Buffer.Length, 0)

Str_Message += ASCII.GetString(Byte_Buffer, 0, Int_Bytes)

If (Int_Bytes < Byte_Buffer.Length) Then

Exit Do

End If

Loop

Arr_Msg = Str_Message.Split(Sep)

If (Str_Message.Length > 2) Then

Str_Message = Arr_Msg(Arr_Msg.Length - 2)

Else

Str_Message = Arr_Msg(0)

End If

If (Not (Str_Message.Substring(3, 1).Equals(" "))) Then

Return ServerReply(True)

End If

Return Str_Message

End Function

Private Sub SendCommand(ByVal Str_Command As String)

Str_Command = Str_Command & ControlChars.CrLf

Dim cmdbytes As Byte() = ASCII.GetBytes(Str_Command)

Obj_ClientSocket.Send(cmdbytes, cmdbytes.Length, 0)

End Sub