Private Sub Com_Send_Click()
Dim h
If Com_Send.Caption = "发送文件" Then
        If FileLen > 0 And FilePath <> "" Then
           For h = 0 To Winsock2.UBound
               Winsock2(h).SendData UTF8_Encode("101")
               Winsock2(h).SendData UTF8_Encode(filename)
               Com_Send.Caption = "取消发送"
               SendFile.Text = "正在等待对方响应......"
               FileSend = True
        Else-----------------------------------此行出错
            MsgBox "尚未选择文件或文件长度为零", 64, "提示"
        End If
    Else
        MsgBox "请先建立连接!", 64, "提示"
Else
    Winsock2.SendData UTF8_Encode("255")
    FileSend = False
    Com_Send.Caption = "发送文件"
    Label4 = "工作状态:空闲"
End If
End Sub

for 循环没结束。

Private Sub Com_Send_Click()
Dim h
If Com_Send.Caption = "发送文件" Then
        If FileLen > 0 And FilePath <> "" Then
           For h = 0 To Winsock2.UBound
               Winsock2(h).SendData UTF8_Encode("101")
               Winsock2(h).SendData UTF8_Encode(filename)
               Com_Send.Caption = "取消发送"
               SendFile.Text = "正在等待对方响应......"
               FileSend = True
            '这里没有循环结束语句 Next h
        Else-----------------------------------此行出错
            MsgBox "尚未选择文件或文件长度为零", 64, "提示"
        End If
    Else    '这个 Else 没有对应的 If 及 End If 语句
        MsgBox "请先建立连接!", 64, "提示"
Else
    Winsock2.SendData UTF8_Encode("255")
    FileSend = False
    Com_Send.Caption = "发送文件"
    Label4 = "工作状态:空闲"
End If
End Sub

有个VB外挂程式他会帮你把每个区块用线串起来