使用gsm调制解调器mmx610u发送短信

Question

我有一个GSM调制解调器（mmx610u）连接到我服务器的USB端口。

我使用以下代码发送短信。代码工作正常，但当有多个收件人时，短信仅发送给前1或2个收件人。

请建议我，代码中有什么问题？

Public Shared Function SendSMSMobile(ByVal MobNo As String, ByVal MessageBody As String) As Boolean
    Dim pNo As String() = New String(-1) {}
    Dim IsSend As Boolean = False
    Try
        Dim PortNo As String = ""
        Dim mos As New ManagementObjectSearcher("SELECT * FROM Win32_POTSModem")
        For Each mo As ManagementObject In mos.[Get]()
            Dim COMPort As String = mo("AttachedTo").ToString()
            Dim command As [String] = "AT"
            Dim serialPort As SerialPort = Nothing
            Try
                serialPort = New SerialPort()
                serialPort.PortName = COMPort
                serialPort.BaudRate = 9600
                serialPort.DataBits = 8
                serialPort.Parity = Parity.None
                serialPort.ReadTimeout = 300
                serialPort.WriteTimeout = 300
                serialPort.StopBits = StopBits.One
                serialPort.Handshake = Handshake.None
                serialPort.Open()
                If serialPort.IsOpen = True Then
                    PortNo = COMPort
                    Array.Resize(pNo, pNo.Length + 1)
                    pNo(pNo.Length - 1) = PortNo
                End If
            Catch
            Finally
                serialPort.Close()
                serialPort.Dispose()
            End Try
        Next

        If PortNo.Trim().Length > 0 Then
            If MobNo.Substring(0, 1) = "0" AndAlso MobNo.Length > 5 Then
                MobNo = MobNo.Substring(1, MobNo.Length - 1)
            End If
            If MobNo.Trim().Length >= 10 AndAlso PortNo.Length > 0 Then
                Dim MsgLength As Integer = Convert.ToInt32(MessageBody.Length)
                Dim Q__1 As Integer = MsgLength \ 260
                Dim R As Integer = MsgLength Mod 260
                If R > 0 Then
                    Q__1 = Q__1 + 1
                End If
                For i As Integer = 0 To Q__1 - 1
                    Dim StartIndex As Integer = i * 260
                    Dim EndIndex As Integer = 260
                    If i = Q__1 - 1 Then
                        EndIndex = R
                    End If
                    Dim Msg As String = MessageBody.Substring(StartIndex, EndIndex)
                    Dim sp As New SerialPort()

                    For q As Integer = 0 To pNo.Length - 1
                        '#Region "MOBILE"
                        Try
                            Dim arr As Char() = New Char(0) {}
                            arr(0) = ChrW(26)
                            sp.PortName = pNo(q).ToString()
                            sp.BaudRate = 96000
                            sp.Parity = Parity.None
                            sp.DataBits = 8
                            sp.StopBits = StopBits.One
                            sp.Handshake = Handshake.XOnXOff
                            sp.DtrEnable = True
                            sp.RtsEnable = True
                            sp.NewLine = Environment.NewLine
                            sp.Open()
                            Dim mSpeed As Integer = 2000
                            sp.Write("AT+CMGF=1" + Environment.NewLine)
                            System.Threading.Thread.Sleep(200)

                            sp.Write("AT+CSCS=GSM" + Environment.NewLine)
                            System.Threading.Thread.Sleep(200)
                            sp.Write(("AT+CMGS=" & ChrW(34) & MobNo & ChrW(34)) + Environment.NewLine)
                            System.Threading.Thread.Sleep(200)
                            sp.Write(Msg & ChrW(26))

                            System.Threading.Thread.Sleep(mSpeed)
                            IsSend = True
                        Catch
                            IsSend = False
                        Finally
                            sp.Close()
                            sp.Dispose()
                        End Try
                    Next
                Next
            End If
        End If
    Catch
        IsSend = False
    End Try
    Return IsSend
End Function