Packet

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Afr0	Created : 19 July 2010 Edited : 21 July 2010 System : Server Based Language : C/C++ Packet A generic Packet class
Here's a generic packet class that I just made. I don't know why... but it seems the absence of programming that occured after I quit school has begun to catch up with me ever so slightly! using System; using System.Collections.Generic; using System.IO; using System.Text; namespace iNet { public class Packet { private int m_ID; private int m_Length; private MemoryStream m_Buffer; private BinaryReader m_BufferReader; private BinaryWriter m_BufferWriter; //For people who likes writing code to deal with unneccessary exceptions..! private string m_Username; /// <summary> /// Standard constructor for RECEIVED packets. /// </summary> /// <param name="ID">The ID of the packet.</param> /// <param name="Length">The length of the packet.</param> /// <param name="Data">The data that was received.</param> public Packet(int ID, int Length, byte[] Data) { m_ID = ID; m_Length = Length; m_Buffer = new MemoryStream(Data); m_BufferReader = new BinaryReader(m_Buffer); //If a packet's data is split up across multiple TCP packets, //a received packet might have to be 'spliced' after being created. m_BufferWriter = new BinaryWriter(m_Buffer); } /// <summary> /// Supplemental constructor for RECEIVED packets. /// Only to be used by people who likes writing code /// for dealing with unneccessary exceptions. /// </summary> /// <param name="ID">The ID of the packet.</param> /// <param name="Length">The length of the packet.</param> /// <param name="Data">The data that was received.</param> /// <param name="Username">The username of the person writing code for dealing /// with unnneccessary exceptions.</param> public Packet(int ID, int Length, byte[] Data, string Username) { m_ID = ID; m_Length = Length; m_Username = Username; m_Buffer = new MemoryStream(Data); m_BufferReader = new BinaryReader(m_Buffer); //If a packet's data is split up across multiple TCP packets, //a received packet might have to be 'spliced' after being created. m_BufferWriter = new BinaryWriter(m_Buffer); } /// <summary> /// Standard constructor for OUTGOING packets. /// </summary> /// <param name="ID">The ID of the packet.</param> /// <param name="Length">The length of the packet.</param> public Packet(int ID, int Length) { m_ID = ID; m_Length = Length; m_Buffer = new MemoryStream(); m_BufferWriter = new BinaryWriter(m_Buffer); } /// <summary> /// Supplemental constructor for OUTGOING packets. /// Only to be used by people who likes writing code /// for dealing with unneccessary exceptions. /// </summary> /// <param name="ID">The ID of the packet.</param> /// <param name="Length">The length of the packet.</param> /// <param name="Username">The username of the person writing code for dealing /// with unnneccessary exceptions.</param> public Packet(int ID, int Length, string Username) { m_ID = ID; m_Length = Length; m_Username = Username; m_Buffer = new MemoryStream(); m_BufferWriter = new BinaryWriter(m_Buffer); } #region Reading /// <summary> /// Peeks an Int32 from the Packet's internal buffer. /// </summary> /// <param name="PositionFromBeginning">The position within the buffer to start peeking.</param> /// <returns>The Int32 that was peeked.</returns> public virtual int PeekInt32(long PositionFromBeginning) { int Value = 0; try { long OriginalPosition = m_Buffer.Position; m_Buffer.Seek(PositionFromBeginning, SeekOrigin.Begin); Value = BitConverter.ToInt32(m_BufferReader.ReadBytes(4), 0); m_BufferWriter.Write(Value); //Should this be SeekOrigin.Current?! m_Buffer.Seek(OriginalPosition, SeekOrigin.Begin); return Value; } catch (Exception E) { Console.WriteLine("Couldn't read from packetbuffer (PeekInt32)!"); Console.WriteLine("\n" + E.ToString()); if (m_Username == "JL235" \|\| m_Username == "DiablosDevil" \|\| m_Username == "Cower") throw new Exception(); return 0; } } /// <summary> /// Overload for BinaryReader.ReadString(). /// Reads a 'regular' string from the Packet's /// buffer. /// </summary> /// <returns>The string that was read.</returns> public virtual string ReadString() { if(m_Buffer.CanRead) return m_BufferReader.ReadString(); return ""; } /// <summary> /// Reads a specific number of characters from the Packet's /// buffer and returns them as a string. /// </summary> /// <param name="NumChars">The number of characters to read.</param> /// <returns>All the characters as a string.</returns> public virtual string ReadString(int NumChars) { string ReturnStr = ""; if(m_Buffer.CanRead) { for (int i = 0; i <= NumChars; i++) ReturnStr = ReturnStr + m_BufferReader.ReadChar(); } return ReturnStr; } public virtual byte ReadByte() { try { return m_BufferReader.ReadByte(); } catch (Exception E) { Console.WriteLine("Couldn't read from packetbuffer (Packet.ReadByte())!"); Console.WriteLine("\n" + E.ToString()); if (m_Username == "JL235" \|\| m_Username == "DiablosDevil" \|\| m_Username == "Cower") throw new Exception(); //Could have just returned 0 as a standard value if m_Buffer doesn't //support reading, but this way at least we have some debug info to //go along with it, seeing as 0 could be a valid value on a call to //this method. return 0; } } public virtual short ReadInt16() { try { return m_BufferReader.ReadInt16(); } catch (Exception E) { Console.WriteLine("Couldn't read from packetbuffer (Packet.ReadInt16())!"); Console.WriteLine("\n" + E.ToString()); if (m_Username == "JL235" \|\| m_Username == "DiablosDevil" \|\| m_Username == "Cower") throw new Exception(); //Could have just returned 0 as a standard value if m_Buffer doesn't //support reading, but this way at least we have some debug info to //go along with it, seeing as 0 could be a valid value on a call to //this method. return 0; } } public virtual int ReadInt32() { try { return m_BufferReader.ReadInt32(); } catch (Exception E) { Console.WriteLine("Couldn't read from packetbuffer (Packet.ReadInt32())!"); Console.WriteLine("\n" + E.ToString()); if (m_Username == "JL235" \|\| m_Username == "DiablosDevil" \|\| m_Username == "Cower") throw new Exception(); //Could have just returned 0 as a standard value if m_Buffer doesn't //support reading, but this way at least we have some debug info to //go along with it, seeing as 0 could be a valid value on a call to //this method. return 0; } } public virtual long ReadInt64() { try { return m_BufferReader.ReadInt64(); } catch (Exception E) { Console.WriteLine("Couldn't read from packetbuffer (Packet.ReadInt64())!"); Console.WriteLine("\n" + E.ToString()); if (m_Username == "JL235" \|\| m_Username == "DiablosDevil" \|\| m_Username == "Cower") throw new Exception(); //Could have just returned 0 as a standard value if m_Buffer doesn't //support reading, but this way at least we have some debug info to //go along with it, seeing as 0 could be a valid value on a call to //this method. return 0; } } #endregion #region Writing //Note: The MemoryStream class is expansive by nature, so //therefore it should theoretically be no limit on how much //to write into the Packet's buffer. Which is why there is no //error checking in any of these methods. No sane programmer //would design a packet > 1 megabyte anyways... /// <summary> /// Overload for BinaryWriter.Write(string value). /// Writes a string to the Packet's buffer. /// </summary> /// <param name="Str">The string to write.</param> public virtual void WriteString(string Str) { m_BufferWriter.Write(Str); } /// <summary> /// Overload for BinaryWriter.Write(string value). /// Writes a string to the Packet's buffer, but takes /// the Packet's size into account. If the string /// can't fit within the intended length, it will NOT /// be written! /// </summary> /// <param name="Str">The string to write.</param> public virtual void WriteStringSafe(string Str) { if ((m_Buffer.Length + Str.Length) <= m_Length) { m_BufferWriter.Write(Str); } else { Console.WriteLine("Tried to write beyond packet's size! (WriteStringSafe())"); if (m_Username == "JL235" \|\| m_Username == "DiablosDevil" \|\| m_Username == "Cower") throw new Exception(); } } /// <summary> /// Overload for BinaryWriter.Write(byte value). /// </summary> /// <param name="Value">The byte to write.</param> public virtual void WriteByte(byte Value) { m_BufferWriter.Write(Value); } /// <summary> /// Overload for BinaryWriter.Write(byte value). /// Writes a byte to the Packet's buffer, but takes /// the Packet's size into account. If the byte /// can't fit within the intended length, it will NOT /// be written! /// </summary> /// <param name="Str">The byte to write.</param> public virtual void WriteByteSafe(byte Value) { if ((m_Buffer.Length + 1) <= m_Length) { m_BufferWriter.Write(Value); } else { Console.WriteLine("Tried to write beyond packet's size! (WriteByteSafe())"); if (m_Username == "JL235" \|\| m_Username == "DiablosDevil" \|\| m_Username == "Cower") throw new Exception(); } } /// <summary> /// Overload for BinaryWriter.Write(byte[] buffer). /// </summary> /// <param name="Data">The byte array to write.</param> public virtual void WriteBytes(byte[] Data) { m_BufferWriter.Write(Data); } /// <summary> /// Overload for BinaryWriter.Write(byte[] buffer). /// Writes an array of bytes to the Packet's buffer, /// but takes the Packet's size into account. If /// the array can't fit within the intended length, /// it will NOT be written! /// </summary> /// <param name="Str">The byte to write.</param> public virtual void WriteBytesSafe(byte[] Data) { if ((m_Buffer.Length + Data.Length) <= m_Length) { m_BufferWriter.Write(Data); } else { Console.WriteLine("Tried to write beyond packet's size! (WriteBytesSafe())"); if (m_Username == "JL235" \|\| m_Username == "DiablosDevil" \|\| m_Username == "Cower") throw new Exception(); } } /// <summary> /// Overload for BinaryWriter.Write(int value). /// </summary> /// <param name="Value">The int to write.</param> public virtual void WriteInt32(int Value) { m_BufferWriter.Write(Value); } #endregion public int PacketID { get { return m_ID; } } public int PacketLength { get { return m_Length; } } } } --v If I may say so myself, this is, aside from being a perfectly functioning Packet class, a good example of OOP. So for people like Jay who are afraid of OOP, this might be worth studying!

Comments
Monday, 19 July 2010, 06:47
Jayenkai	Not worth studying.. Too Scary!!!! It's even got error messages, and everything! AARRGGHH!!
Monday, 19 July 2010, 10:02
Afr0	Update: Added some methods for writing safely to the packet's buffer, I.E taking the packet's length into account.
Tuesday, 20 July 2010, 15:10
Afr0	Update: Added a method for peeking Int32s from the packet's buffer. If you need to peek some other types, you should have no problem coming up with a method yourself from looking at the code.
Tuesday, 20 July 2010, 21:53
JL235	I would advise having methods throw exceptions rather then write to the command line. If I call 'PeekInt32' I am not expecting it to perform printing.
Wednesday, 21 July 2010, 07:51
Afr0	That is a question of design. Making unique exceptions for classes to throw, or even just throwing a standard exception, means the user has to write code to handle those exceptions. I prefer to handle the exceptions within the methods.
Wednesday, 21 July 2010, 08:09
JL235	Ok, then lets say I use your code and a packet I am reading is incorrect. As a developer, how can I be informed my packet is incorrect and so write code to deal with it (like ask for the packet to be resent) when the error is being printed to the console?
Wednesday, 21 July 2010, 09:05
Afr0	Quite frankly I wrote this code to be used for a server application. Server applications should be console apps, not Window(s) apps. That said, when developing a networked application you end up looking at data sent through the wire all the time in some form or another. The chance that you will not know if a packed received didn't contain all the data it was supposed to contain is remote. And even if it didn't contain all the data, that is more than likely a problem with the way you're receiving or sending the data rather than a problem with the way you're reading the received data from the packet. The reason I even bothered to catch exceptions at all was as a last-resort thing rather than a 'end all be all' of my network infrastructure.
Wednesday, 21 July 2010, 09:14
Afr0	Update: Added code to ensure that people who likes writing code for dealing with unneccessary exceptions can do just that!
Wednesday, 21 July 2010, 09:29
JL235	Afr0 Quite frankly I wrote this code to be used for a server application. Server applications should be console apps Actually most server apps are background programs, neither console or window. So in practice any error output sent to the console will just be lost. Saving to a log file more common and this also means you automatically have this saved on disk. No one is going to have a console open permanently whilst the WoW servers are running. It'll mean the app is dependent on the terminal being open, which in turn is dependent on someone being constantly connected to the machine. If they lose their connection then the server will go down too (as it's running from their terminal session which would have closed).
Wednesday, 21 July 2010, 17:13
Afr0	Actually most server apps are background programs, neither console or window. So in practice any error output sent to the console will just be lost. Saving to a log file more common and this also means you automatically have this saved on disk. No one is going to have a console open permanently whilst the WoW servers are running. It'll mean the app is dependent on the terminal being open, which in turn is dependent on someone being constantly connected to the machine. If they lose their connection then the server will go down too (as it's running from their terminal session which would have closed). Most server emus are not background apps, but console apps. But I see your point. It really comes down to whether you are physically or remotely controlling your server. I know Blizzard are physically controlling their servers, for instance, as they have a serverfarm in EU and North America. So the WoW server app could be a console app.
Thursday, 22 July 2010, 00:15
JL235	Being able to open up a terminal and interact with their server software is not the same as running the software itself directly within a remote console. They might start it from a console, but it'll be spawned to go off and run on it's own so that the user can close their console. It just doesn't make sense to have such important software running directly within a users console.
Friday, 23 July 2010, 21:38
Afr0	They might start it from a console, but it'll be spawned to go off and run on it's own so that the user can close their console. Why should the user close their console? Why should they do anything else but use the console? The server is supposed to be dedicated, I.E not used for anything but running the serversoftware and act as a terminal through which to operate it.
Saturday, 24 July 2010, 08:02
JL235	Afr0 Why should the user close their console? Because they will want to disconnect from the server. Hundreds of reasons why they would want to disconnect.
Saturday, 24 July 2010, 13:24
Stealth	Then just run it as a process on the server instead of a console application. The way Afr0 is doing it isn't that big of a deal.

Comments