Packeting and Tokenizing TCP/IP

TalonSnow · 2005-05-05T15:21:16

Ok so I am redoing my message handling on my server and client, however I am confused on best way to implament this. I have read through a dozen tutorial and faq's and here is my current ideas, and where I see them fail, as well as an idea on how to proceed. Please give any suggestions (or flames) on how it wont or will work. (1) I was thinking of making a struct to hold 4 bytes for length sending, 4 bytes for message ID and then a char* for the message. Then sending this over to the other end. However I came across two problems this way. (a) on the receiving end there is no way (that i can see) to pull out the correct size of the struct, to gain access to the length field. I was thinking of sizeof(struct) but that would only return 8 bytes as the char* would only be described as 4 bytes. So how would I recieve the entire struct? so on to (2) A char* with 4 bytes describign length 4 bytes on messageid then following is the message. Then I test if the incoming is leftover data needed to complete last message, or a new one. If new one i pull out length, and message id, then parse through the message 1 char at a time transfering it into a vector, until len has been reached. If any is left over, then a int value is assigned with remander and waits for next receive to pull in rest. here is example flowchart. receive char* msg if (new message) //msglength equals 0 pull out first 4 bytes and assign to length pull out next 4 bytes and assign to messageID make messagelength equal to length loop through from 0 to end of message pulling in each character and reducing messagelength if (finish message) //msglength > 0 loop through from 0 till msglength equals 0 if length > msglength then goto new message Ok, now the problem with this is, what happens if the finished message ends near the end of the receving message, and the new message only starts with the first 4 bytes? Then it would all fail as you wouldnt be reading in the 4 bytes for messageID and instead it would treat that as par tof the message. This would very very infrequent happen, but could, if im right. So you would start to have to add in alot more checks (3) Do like most do and just assign a base size to the buffer, however what if you wanted less than this or more? so lastly my idea that I havent tried (4) linked lists Can you have a linked list where each "record" had a length and buffer and a link. then first full message would be assigned to the buffer in the linked list, and the size of it, then the first 4 bytes would be retrieved finding out the size fo the full message. If the full size is within the inital message then it is parsed accordingly, then checks to see if a new message is also started in initial message. If the message is not fully completed, then the next receive is made into the next record, and the first is linked to it, again checking for the full message. Once the message is compelted, the records containing the first messages are all deleted and the record with new message started remains, and the head is now linked to this. This way you can have a message a slarge as you want and only memory your using up is what is acually holding data. So will this work? Or am i missing an easier way or wrong about a previously mentioned one? please help teach me :)

Networking and Multiplayer Programming

Started by TalonSnow May 02, 2005 04:50 PM

9 comments, last by TalonSnow 19 years, 9 months ago

TalonSnow

Author

128

May 05, 2005 03:21 PM

ok I will mike, thanks for continuing to help me through this also and not giving up! :)

One thing i noticed as well this morning was I stepped through the code on client and server trying to catch anything wrong. And outputting as much as i could for debugging. It seems the server is sending the values as they should be and they dont change at anypoint, including after the call to send.
However, on the receiving side, once I pull in the header correctly the call to receive the data does return a value of 15 on byte size that got received, but checking the value asscoiated with the data while debugging, showed a 0.

I changed my void* for my data to a char* instead and had the receiving side just do:
p.data = new char[p.h.size];
then call the receive for the characters

2 things occured.
(1) i got an error saying "cannot convert from 'unsigned int *_w64' to 'size_t'
"
(2) still getting a 0 when receiving the 15 bytes

with regards to 1, is this right to have it as a _w64? could this be my problem in why i am havign to have to do a ntohs on my header values i pull out on the receiving end?

<=- Talon -=>

Packeting and Tokenizing TCP/IP

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Packeting and Tokenizing TCP/IP

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