MultiSync - sending char values error

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CheatCat

17

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Joined: 7th Mar 2007

Location: Sweden

Posted: 17th Jul 2008 21:02

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Well, I try to send some text from the host to client, but I only get this error:

+ Code Snippet

Unhandled exception at 0x100048c9 in Host.exe: 0xC0000005: Access violation writing location 0x00000000.

Here is the host code:

+ Code Snippet

#include <DarkGDK.h>
#include "multisync.h"

int counter = 0;
char* playername[2];

void DarkGDK ( void )
{
	dbSyncOn();
	playername[0] = "Host";
	
	if (NetHost(16))
	{
		while (LoopGDK())
		{
				if (NetPlayerJoined() != 0)
				{
					counter++;
				}
				
				if (counter > 0)
				{
					while(NetGetMessage() == true)
					{
						NetGetString(playername[1], 80);
					}
					
					NetPutString(playername[0]);

					NetSendAll();
				}
			dbSync();
		}
	}
}

And the client:

+ Code Snippet

#include <DarkGDK.h>
#include "multisync.h"

char* playername[2];

void DarkGDK ( void )
{
	dbSyncOn();
	playername[1] = "Client";
	
	if (NetConnect("127.0.0.1"))
	{
		while (LoopGDK())
		{
			while(NetGetMessage() == true)
			{
				NetGetString(playername[0], 80);
			}
					
			NetPutString(playername[1]);

			NetSendAll();
			dbSync();
		}
	}
}

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Benjamin

21

Years of Service

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Joined: 24th Nov 2002

Location: France

Posted: 17th Jul 2008 21:47 Edited at: 17th Jul 2008 21:48

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This is your problem

+ Code Snippet

NetGetString(playername[1], 80);

You haven't allocated any space to store the returned string data.

Multisync - TCP Server/Client Multiplayer Plugin (DBP/DBCe)

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CheatCat

17

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Joined: 7th Mar 2007

Location: Sweden

Posted: 19th Jul 2008 19:51

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And my dumb question is: How I allocate space to store the string?

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Benjamin

21

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Joined: 24th Nov 2002

Location: France

Posted: 19th Jul 2008 21:18 Edited at: 19th Jul 2008 21:20

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See this on dynamic memory allocation. What you need to do is use the new operator to allocate memory, and store the pointer it returns. For example:

+ Code Snippet

char * playerName = new char[numberOfBytes];

Always make sure the buffer is big enough to store the data you want to put in it, and remember to account for the fact that you need an extra byte to store the zero character at the end of a string.

When you no longer need the buffer, you can free it using delete. Note that you need to specify brackets before the variable name if you allocated multiple items (which in this case you are):

+ Code Snippet

delete [] playerName;
playerName = NULL; Set the pointer to NULL so we can later check if the buffer is allocated

Multisync - TCP Server/Client Multiplayer Plugin (DBP/DBCe)

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CheatCat

17

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Joined: 7th Mar 2007

Location: Sweden

Posted: 20th Jul 2008 20:33

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But how I do if I whant to store more than one value in the playername array?

I have tried with this:

+ Code Snippet

char* playername[2] = new char[80];

And I get this error:

+ Code Snippet

error C2440: 'initializing' : cannot convert from 'char *' to 'char *[17]'

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CheatCat

17

Years of Service

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Joined: 7th Mar 2007

Location: Sweden

Posted: 21st Jul 2008 20:43

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I get it!

Almost... :S

Host:

+ Code Snippet

#include <DarkGDK.h>
#include "multisync.h"

int counter = 0;
char* playername[2];

void DarkGDK ( void )
{
	dbSyncOn();
	playername[0] = "Host";
	
	if (NetHost(16))
	{
		while (LoopGDK())
		{
				if (NetPlayerJoined() != 0)
				{
					counter++;
				}
				
				if (counter > 0)
				{
					while(NetGetMessage() == true)
					{
						playername[1] = new char[100];
						NetGetString(playername[1], 80);
					}
					
					NetPutString(playername[0]);

					NetSendAll();
				}
			dbSync();
		}
	}
}

Client:

+ Code Snippet

#include <DarkGDK.h>
#include "multisync.h"

char* playername[2];

void DarkGDK ( void )
{
	dbSyncOn();
	playername[1] = "Client";
	
	if (NetConnect("127.0.0.1"))
	{
		while (LoopGDK())
		{
			while(NetGetMessage() == true)
			{
				playername[0] = new char[100];
				NetGetString(playername[0], 80);
			}
					
			NetPutString(playername[1]);

			NetSendAll();
			dbSync();
		}
	}
}

But I get an popup with this error:
"Message full, cannot write."

Should I empty the char array, and how?

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haYnguy

16

Years of Service

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Joined: 5th Jun 2008

Location: on my island

Posted: 27th Jul 2008 07:00

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No, you need to do NetSend(0) after NetSendAll(); to clear out the message buffer.

-- from my island, aloha wau 'ia 'oe --

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Dark GDK / MultiSync - sending char values error