Python - creating byte arrays help

Hi

I have my TCP connection, server listen code fleshed out.
On the client, though,
I'd like to create a byte array of a certain length, with a tag number.
How do I do this?
basically Java,

byte[] data = new byte[500] // is that the correct size for a TCP network game HELO message? smaller? can be 3 . . .
data[0] = HELO_MSG byte
data[1] = client number byte #1
data[2] = client number byte #2
That's all? no need for more than 256 clients..so, one byte.
The client port, address, etc is gathered from this message.
I can send and listen, but I don't know how to create a blank byte[] of x size and fill it with certain numbers?
byte[] data = new byte[3]
What about in game messages, that can be hundreds of bytes?
LVL 1
beavoidAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

beavoidAuthor Commented:
I found this, that worked over TCP.
s.sendall(b'Hello, world')

Open in new window


Is that right? It didn't explode.
How do I make a bigger byte array for in-game messages? Or are they not big. I'm thinking big because of movements of large numbers of units. Must I keep groupings of units registered in the server?
How can I set the size of each type of message byte array?
Incidentally, when I hardcoded the byte array, my other socket explosions stopped.
0
peprCommented:
Yes. The b'whatever' (with the b prefix is a literal of the bytes type. It looks like a string literal but the difference is that no encoding is considered. Which is fine if you use ASCII of if you want to use the same encoding for sending the messages as used in the Python source code.

In Python 2, the bytes was the same as the str type. In Python 3, the two types are separated. Python strings are more abstract, and you have to tell the encoding to convert them to bytes (https://docs.python.org/3.3/library/functions.html?highlight=bytes#bytes)

The bytes type is immutable (as also strings are). If you need some extra manipulation -- such as appending other bytes to the message before sending it -- use the bytearray type (https://docs.python.org/3.3/library/functions.html?highlight=bytes#bytearray):
msg = bytearray(b'Hello, world ')
msg.append(0x34)   # just coincicence -- ordinal number of '4'
msg.append(0x32)   # ordinal number of '2'
print(msg)
s.sendall(msg)

Open in new window

0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
beavoidAuthor Commented:
Thanks

bytearray is the answer

am doing

data=bytearray(5)
data[0]= MSG_HELO

and it sends this over TCP the same.
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Computer Games

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.