FTP服务器连接及状态--vb.net

代码有注解。看不懂请留言。

Imports System.IOImports System.NetImports System.Net.SocketsImports System.ThreadingImports System.TextPublic Class Form1    Private timeoutObject As ManualResetEvent    Private ssocket As Socket    Private isConn As Boolean        Public Function CheckFtp(ByVal ip As String, ByVal ftpuser As String, ByVal ftppas As String, ByRef errmsg As String, Optional port As Integer = 21, Optional timeout As Integer = 2000) As Boolean        '*********输入数据检查开始*********        If ftpuser.Trim.Length = 0 Then            errmsg = "FTP用户名不能为空,请检查设置!"            Return False        End If        If ftppas.Trim.Length = 0 Then            errmsg = "FTP密码不能为空,请检查设置!"            Return False        End If        Dim address As IPAddress = Nothing        Try            address = IPAddress.Parse(ip)        Catch ex As Exception            errmsg = String.Format("FTP服务器IP:{0}解析失败,请检查是否设置正确!", ip)            Return False        End Try        '*********输入数据检查结束*********        isConn = False        Dim ret As Boolean = False        Dim result(1024) As Byte        '连接返回,用户名返回,密码返回,退出返回        Dim pingStatus As Integer = 0        Dim userStatus As Integer = 0        Dim pasStatus As Integer = 0        Dim exitStatus As Integer = 0        timeoutObject = New ManualResetEvent(False)        Try            Dim receivelength As Integer            ssocket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)            ssocket.SendTimeout = timeout            ssocket.ReceiveTimeout = timeout            Try                ssocket.BeginConnect(New IPEndPoint(address, port), New AsyncCallback(AddressOf callBackMethod), ssocket)                If timeoutObject.WaitOne(timeout, False) = False Then '阻止当前线程                    ssocket.Close()                    ssocket = Nothing                    pingStatus = -1 '超时返回状态码-1，并返回false值                End If                If isConn = True Then '连接状态                    pingStatus = 200                Else                    pingStatus = -1                End If            Catch ex As Exception                pingStatus = -1            End Try            If pingStatus = 200 Then '状态码200 - TCP连接成功                receivelength = ssocket.Receive(result)                pingStatus = getFtpReturnCode(result, receivelength) ' 连接状态                If pingStatus = 220 Then '状态码220 - FTP返回欢迎语                    ssocket.Send(Encoding.Default.GetBytes(String.Format("{0}{1}", "USER " + ftpuser, Environment.NewLine)))                    receivelength = ssocket.Receive(result)                    userStatus = getFtpReturnCode(result, receivelength)                    If userStatus = 331 Then                        ssocket.Send(Encoding.Default.GetBytes(String.Format("{0}{1}", "PASS " + ftppas, Environment.NewLine)))                        receivelength = ssocket.Receive(result)                        pasStatus = getFtpReturnCode(result, receivelength)                        If pasStatus = 230 Then                            errmsg = String.Format("FTP:{0}@{1}登陆成功", ip, port)                            ret = True                            ssocket.Send(Encoding.Default.GetBytes(String.Format("{0}{1}", "QUIT", Environment.NewLine))) '登出FTP                            receivelength = ssocket.Receive(result)                            exitStatus = getFtpReturnCode(result, receivelength)                        Else                            errmsg = String.Format("FTP:{0}@{1}登陆失败,用户名或密码错误({2})", ip, port, pasStatus) '状态码230的错误                        End If                    Else                        errmsg = String.Format("使用用户名:'{0}'登陆FTP:{1}@{2}时发生错误({3}),请检查FTP是否正常配置!", ftpuser, ip, port, userStatus) '状态码331的错误                    End If                Else                    errmsg = String.Format("FTP:{0}@{1}返回状态错误({2}),请检查FTP服务是否正常运行!", ip, port, pingStatus) '状态码220的错误                End If            Else                errmsg = String.Format("无法连接FTP服务器:{0}@{1},请检查FTP服务是否启动!", ip, port) '状态码200的错误            End If        Catch ex As Exception            '连接出错            errmsg = String.Format("FTP:{0}@{1}连接出错:", ip, port) + ex.Message            'Common.logger(errmsg) '写日志            ret = False        Finally            If ssocket IsNot Nothing Then                ssocket.Close() '关闭socket                ssocket = Nothing            End If        End Try        Return ret    End Function    Private Sub callBackMethod(ByVal asyncResult As IAsyncResult)        Try            ssocket = asyncResult.AsyncState            If ssocket IsNot Nothing Then                ssocket.EndConnect(asyncResult)                isConn = True            End If        Catch ex As Exception            isConn = False        Finally            timeoutObject.Set()        End Try    End Sub    ''' <summary>    ''' 传递FTP返回的byte数组和长度,返回状态码(Integer)    ''' </summary>    ''' <param name="retByte"></param>    ''' <param name="retLen"></param>    ''' <returns></returns>    ''' <remarks></remarks>    Private Function getFtpReturnCode(ByVal retByte() As Byte, ByVal retLen As Integer) As Integer        Try            Dim str As String = Encoding.ASCII.GetString(retByte, 0, retLen).Trim            MsgBox(Encoding.UTF8.GetString(retByte)) '查看每次返回情况            Return Integer.Parse(str.Substring(0, 3))        Catch ex As Exception            Return -1        End Try    End FunctionEnd Class