|
Hi guys!
I got a general problem here with UDP multicasts not reaching the server I want to reach.
Perhaps there's a general misconception on my side, perhaps it's just a configuration thing, hope someone can help me out.
I want to create a dynamic service discovery. A client wants to use a service, but doesn't know which server is offering the service.
So I developed a class a service process can use to listen for service discovery requests on a given port and another class for the client to find these services. For this to work I thought I'd use UDP multicasts.
The service joins a multicast group (I've tried 224.0.0.1, 225.0.0.1, 225.1.1.1 and a few more), the client sends a datagram to one of these IP adresses, the service receives the datagram and can reply with an "I'm here" response.
This works fine if I try it within my LAN, but doesn't work if the server and client are located in different subnets. These subnets are connected via a VPN with Zyxel ZyWalls (the ZyWalls are capable of IP multicast according to the specs), yet the packets don't seem to reach the service.
If I don't send the request to a multicast address but use a subnet-specific broadcast or the real target IP, the service gets notified, but that's not what I need - I don't want to make any assumption on the subnet a service is on.
I thought multicast groups were especially designed for such a scenario? According to the documentation I found, members of multicast groups don't have to be part of the same network, so it looks like a routing problem. But unfortunately I don't have any idea what to modify to allow multicast packages to be routed to the other subnets.
Can anyone help?
Thanks in advance,
mav
--
Black holes are the places where God divided by 0...
|
|
|
|
|
Hi
I am trying to check if a file is being written by another process.
I am using teh FileInfo (size) to see if the size (it is a log file) is changing.
When another process is writing to the file my application is stuck.
string fPath = @"c:\temp\build.log";<br />
FileInfo FI = new FileInfo(fPath);<br />
while (1>0)<br />
{<br />
if (lastvalue - FI.Length == 0)<br />
{<br />
iCounter++;<br />
lastvalue = FI.Length;<br />
if (iCounter > 20)<br />
{<br />
MessageBox.Show("times up");<br />
break;<br />
}<br />
<br />
}<br />
else<br />
iCounter = 0;<br />
lastvalue = FI.Length;<br />
<br />
<br />
Thread.Sleep(SleepTime);<br />
}
Any idea could help.
Have a nice Day
|
|
|
|
|
Hi!
One idea that's working fine in some of my programs is trying to open the target file exclusively (with FileShare.None).
If the file can be opened, no other process is accessing the file and thus the file has been created completely. If you get an IOException then sleep for a few ms and try again. Just don't forget to close the file afterwards and include a timeout mechanism so your program doesn't lock up if the file isn't closed because of a bug in the other application.
Regards,
mav
--
Black holes are the places where God divided by 0...
|
|
|
|
|
Thanks for the quick reply.
I understand your suggestion but the problem is that the process holding the file is loading a message box and until i press "ok" the file is still open by it.
The messagebox is not always present .
I want to get a message when the file is not updated anymore .
Have a nice Day
|
|
|
|
|
I fear you're out of luck in this case.
As long as the file is held open by the other application, this other application is free to modify the contents of the file at any given time. So you can never be sure that the other app will not write anything to the file. Depending on the architecture of the other app it could very well be that a background thread still writes to the file even though a message box is being displayed.
Regards,
mav
--
Black holes are the places where God divided by 0...
|
|
|
|
|
Hi use the FileSystemWatcher class
|
|
|
|
|
Thanks a lot i will try
Have a nice Day
|
|
|
|
|
Hi,
I would like to stream the desktop image of one computer to another, over the internet. My idea is to do a screen capture at regular intervals, and send it to the receiver.
In order to reduce network load, I would like to compress each frame in function of the previous one (i.e., only the parts of the picture that have changed between two successive frames should be sent, and those parts are compressed before sending).
I suppose there must be an easy way (e.g., using a codec) to do this, but I can't seem to find it on the web/forums.
Can anyone help me out?
Thanks !
ZeJibe
|
|
|
|
|
There are no easy ways, you have to calc the diff of 2 images yourself.
|
|
|
|
|
Hi,
how i can validate a formula.
Formula contains columns of table and operators.
if suppose c1,c2,c3 are columns of table, c1 is of type string, cs is decimal and c3 is int.
formula may be a+(b*c),or a*(b/c)
lakshmi
|
|
|
|
|
c1 needs to be turned into a number, with int.TryParse or double.TryParse. Then it will just work. Otherwise, it's not possible.
Christian Graus - Microsoft MVP - C++
"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )
|
|
|
|
|
why DataView.RowFilter is more solwer than DataTable.Select function?
using the following code to test.
class Program
{
const int ROWS_COUNT = 50; // 设置处理数据大小。 单位：w 万
const int ROWS_COUNT_UNIT = 10000; // 数据行单位：万
const double ROWS_TOTAL_COUNT = ROWS_COUNT * ROWS_COUNT_UNIT; // 总循环次数
const double ROWS_SHOW_INFO_LINE = ROWS_TOTAL_COUNT / 10; // 显示进度
private static string SAVE_FILE_NAME = string.Format("{0}w_{1}", ROWS_COUNT.ToString(), DateTime.Now.ToString("yyyyMMddhhmmss"));
private static StringBuilder builder = new StringBuilder(string.Format("ROWS COUNT :{0}w\n", ROWS_COUNT));
private static DataTable mDataTable = null;
private static DataView dv = null;
private static string str = string.Empty;
static void Main(string[] args)
{
// 添加数据行
DateTime start = DateTime.Now;
AddData();
str = string.Format("cost [ {0} ms ] to add [ {1}w ] rows.\n{2}\n",
(DateTime.Now.Subtract(start).TotalMilliseconds.ToString()),
ROWS_COUNT.ToString(),
"----- AddData() END -----\n");
Console.WriteLine(str);
builder.AppendFormat(str);
// 添加 DataTable 的主键
start = DateTime.Now;
AddPrimaryKey(true);
str = string.Format("cost [ {0} ms ] to AddPrimaryKey().\n{1}\n",
(DateTime.Now.Subtract(start).TotalMilliseconds.ToString()),
"----- AddPrimaryKey() END -----\n");
Console.WriteLine(str);
builder.AppendFormat(str);
// 循环进行 10 次数据过滤测试
start = DateTime.Now;
int times = 0;
string enter = string.Empty;
while ((++times) < 11)
{
str = string.Format("running {0} times ...\n", times.ToString());
Console.BackgroundColor = ConsoleColor.Red;
Console.WriteLine(str);
Console.ResetColor();
builder.AppendFormat(str);
Test();
builder.Append("\n\n");
}
str = string.Format("\ncost [ {0} ms ] to WHILE loop.\n",
(DateTime.Now.Subtract(start).TotalMilliseconds.ToString()));
Console.WriteLine(str);
builder.AppendFormat(str);
// 测试结果输入到 文件中
WriteToFile(builder.ToString());
// 提示用户操作
Console.WriteLine("Press any key to continue ...");
Console.ReadLine();
}
///
/// 创建dataTable
///
private static void AddData()
{
Console.WriteLine("Adding data ... ");
mDataTable = null;
mDataTable = new DataTable("test");
DataColumn dc = new DataColumn("index", typeof(double));
dc.DefaultValue = 3000;
mDataTable.Columns.Add(dc);
mDataTable.Columns.Add(new DataColumn("content", typeof(string)));
DateTime start = DateTime.Now;
TimeSpan end;
double rowsCount = ROWS_TOTAL_COUNT + 1;
DataRow row = null;
for (int i = 1; i < rowsCount; i++)
{
if (0 == (i % ROWS_SHOW_INFO_LINE))
{
end = DateTime.Now.Subtract(start);
str = string.Format("Readed {0} rows [ {1} ms]...\n\n", i.ToString(), end.TotalMilliseconds.ToString());
Console.WriteLine(str);
builder.AppendFormat(str);
start = DateTime.Now;
}
// 1000w 数据时，出现了 SystemOutOfMemory 的异常
row = mDataTable.NewRow();
//row["index"] = i;
row["content"] = i.ToString();
mDataTable.Rows.Add(row);
}
mDataTable.AcceptChanges();
Console.Clear();
}
///
/// 添加主键值
///
/// <param name="add" />
private static void AddPrimaryKey(bool add)
{
Console.WriteLine("Adding Primarykey ...");
DateTime start;
if (add)
{
// add PrimaryKey columns
int key = mDataTable.PrimaryKey.Length;
DataColumn[] dcs = new DataColumn[key + 2];
dcs[key + 0] = mDataTable.Columns["index"];
dcs[key + 1] = mDataTable.Columns["content"];
start = DateTime.Now;
mDataTable.PrimaryKey = dcs;
str = string.Format("cost [ {0} ms ] mDataTable.PrimaryKey...\n", (DateTime.Now.Subtract(start).TotalMilliseconds.ToString()));
Console.WriteLine(str);
builder.AppendFormat(str);
}
start = DateTime.Now;
dv = null;
dv = mDataTable.DefaultView;
str = string.Format("cost [ {0} ms ] mDataTable.DefaultView...\n", (DateTime.Now.Subtract(start).TotalMilliseconds.ToString()));
Console.WriteLine(str);
builder.AppendFormat(str);
builder.Append("PrimaryKey Columns Details;\n");
foreach (DataColumn dc in mDataTable.PrimaryKey)
{
builder.AppendFormat("Column Name: \t{0}\nColumn DataType: \t{1}\n", dc.ColumnName, dc.DataType.Name);
}
}
///
/// 数据筛选测试
///
private static void Test()
{
const string CONDITIONS_1 = "index < 80000";
const string CONDITIONS_2 = "index < 80000 or (content LIKE '%200%')";
SelectFromDatatable(CONDITIONS_1);
SelectFromDatatable(CONDITIONS_2);
FilterDataView(CONDITIONS_1);
FilterDataView(CONDITIONS_2);
}
///
/// 将结果记录到文件
///
/// <param name="content" /><文件内容/param>
private static void WriteToFile(string content)
{
try
{
System.IO.StreamWriter sw = new System.IO.StreamWriter(string.Format("{0}.txt", SAVE_FILE_NAME), false, Encoding.UTF8);
sw.Write(content);
sw.Close();
sw = null;
}
catch (Exception exp)
{
System.Diagnostics.Debug.WriteLine(exp.Message);
}
}
///
/// 通过DataTabl.Select 过滤数据
///
/// <param name="condtions" />
private static void SelectFromDatatable(string condtions)
{
DateTime start = DateTime.Now;
start = DateTime.Now;
mDataTable.Select(condtions);
builder.AppendFormat("mDataTable.Select(\"{0}\"):\n\t{1} ms\n", condtions, (DateTime.Now.Subtract(start).TotalMilliseconds.ToString()));
}
///
/// 通过 DataTable.DefaultView.RowFilter 过滤数据
///
/// <param name="conditions" />
private static void FilterDataView(string conditions)
{
DateTime start = DateTime.Now;
start = DateTime.Now;
dv.RowFilter = conditions;
builder.AppendFormat("dv.RowFilter = \"{0}\": \n\t{1} ms\n", conditions, (DateTime.Now.Subtract(start).TotalMilliseconds.ToString()));
}
}
宝剑锋从磨砺出，梅花香自苦寒来
我欲仗剑走天涯
|
|
|
|
|
hi
i am new in c#.net.
i want to move among some records in database
for example go to the first record,last record,next record,previus record
please help me.
somi
|
|
|
|
|
1 - don't use your email as a username, it will get you spam
2 - there are tons of articles on the web on this, you should also buy a book and work through it, if you're new to C++.
All you need to do is store a number to represent the index of the record you want to read, and use that to read a record when a button is pressed.
I answered this same question the other day, worded exactly the same. Was it you ? If so, the reason you didn't understand my answer, is that you need to learn some basics first.
Christian Graus - Microsoft MVP - C++
"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )
|
|
|
|
|
Christian Graus wrote: I answered this same question the other day, worded exactly the same.
Then its valid to just post the same response, but you should at least have replaced C++ with C# in this forum  .
Robert
|
|
|
|
|
Hi Guys,
I'm trying to get into XNA v1.0 (..last time I touched it was Beta 1.) ...So, I'm building myself a terrain loader. Trying to get my Terrain class set up so that it can be given a heightmap file and it can initialize the size of the data array based upon the width & height of the file that is passed to it. Does anyone know of a way(preferrably a simple way) of accepting the path of a jpeg and getting the width and height out of the FileInfo?(I'm making an assumption that is where it is located, but I do not know for a fact)
Welcome my son...Welcome..to the Machine
|
|
|
|
|
System.Drawing.Image.FromFile(jpegpath).Size
Mazy
"This chancy chancy chancy world."
|
|
|
|
|
Thanks for your help, but there is no System.Drawing namespace in the XNA Framework(System.Drawing is the wrapper around the GDI). Does anybody know of a method that doesn't use the GDI+?
Welcome my son...Welcome..to the Machine
|
|
|
|
|
JPEG file yourself, as in the following code:
public static Size GetJpegImageSize(string filename) {
FileStream stream=null;
BinaryReader rdr=null;
try {
stream=File.OpenRead(filename);
rdr=new BinaryReader(stream);
for(; ; ) {
byte code=rdr.ReadByte();
if(code!=0xFF) throw new ApplicationException(
"Unexpected value in file "+filename);
code=rdr.ReadByte();
switch(code) {
case 0xFF:
stream.Position--;
break;
case 0xD0: case 0xD1: case 0xD2: case 0xD3: case 0xD4:
case 0xD5: case 0xD6: case 0xD7: case 0xD8: case 0xD9:
break;
case 0xC0: case 0xC1: case 0xC2: case 0xC3:
case 0xC4: case 0xC5: case 0xC6: case 0xC7:
case 0xC8: case 0xC9: case 0xCA: case 0xCB:
case 0xCC: case 0xCD: case 0xCE: case 0xCF:
ReadBEUshort(rdr);
rdr.ReadByte();
ushort h=ReadBEUshort(rdr);
ushort w=ReadBEUshort(rdr);
return new Size(w, h);
default:
int len=ReadBEUshort(rdr);
stream.Position+=len-2;
break;
}
}
} finally {
if(rdr!=null) rdr.Close();
if(stream!=null) stream.Close();
}
}
private static ushort ReadBEUshort(BinaryReader rdr) {
ushort hi=rdr.ReadByte();
hi<<=8;
ushort lo=rdr.ReadByte();
return (ushort)(hi|lo);
}
A JPEG file contains a lot of packets (with Hufman tables and everything).
The above code does not know much about JPEG, it simply tries to jump from one packet
to the next until it finds one with size info.
|
|
|
|
|
Thanks a TON for that...did you just pull that off the top of your head? Or did you have reference material for that? What information did you refer to?
Welcome my son...Welcome..to the Machine
|
|
|
|
|
Hi,
I once wrote a JPEG file viewer based on the JPEG standard[^].
And today I threw out everything that was not needed when only Size matters...
|
|
|
|
|
...how long did it take you to parse through all of the W3C info to turn it into something useful?
Welcome my son...Welcome..to the Machine
|
|
|
|
|
Actually not very long, I did not read most of the spec, I just looked for the overall
structure (packets with 2B code and 2B length field) and a couple of specifics that did
interest me at the time. And with a simple viewer, I just looked inside a lot of JPEG files
to see what kind of information typically gets included.
BTW a lot of cameras add exposure information (make and model, datetime, image corrections,
etc) to the JPEG files they create, and the Image class allows you to retrieve these
using the getPropertyItem() method.
|
|
|
|
|
...I was thinking that I was going to have to find a way to pull the FileHeader off, store it in the .Net equivalent of a BITMAPFILEHEADER. Then, pull the InfoHeader off of the file and store it in the .NET equivalent of a BITMAPINFOHEADER...& pull the width & height from it
...or by using WMI. That was more along my line of thinking.
Welcome my son...Welcome..to the Machine
|
|
|
|
|
Hi,
The structs you mentioned exist in a .bmp file, not in a JPEG file.
And before you ask, no I dont have a BMP Viewer yet.
As for WMI, I dont think WMI would help looking at JPEGs; it is involved in system resources.
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
