Bananas protocol - how to know if there are any more response packets

[michalc]

This is a follow up to #11863 which I'm making a (very basic) Python client to fetch content from the Bananas content server. And specifically in this case, I would like to fetch an AI by its name.

Nosing around sources in https://github.com/OpenTTD/py-protocol, https://github.com/OpenTTD/bananas-server and https://github.com/OpenTTD/OpenTTD/blob/master/src/network/network_content.cpp, I've figured out how to make a request for the list of published AIs. Very initial code is at michalc/OpenTTDLab#116, but to have it here:

def bananas_file(ai):

    def recv_iter(s, length):
        while length:
            chunk = s.recv(length)
            if not chunk:
                raise Exception("Connection ended")
            length -= len(chunk)
            yield chunk

    def recv_bytes(s, length):
        return b''.join(recv_iter(s, length))

    def recv_packet(s):
        length = struct.unpack("<H", recv_bytes(s, 2))[0]
        return recv_bytes(s, length - 2)

    # Connect
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
    s.settimeout(10.0)
    s.connect(("content.openttd.org", 3978))

    # Send request for AI list
    PACKET_CONTENT_CLIENT_INFO_LIST = 0
    CONTENT_TYPE_AI = 3
    packet_body = \
        struct.pack("<B", PACKET_CONTENT_CLIENT_INFO_LIST) + \
        struct.pack("<B", CONTENT_TYPE_AI) + \
        struct.pack("<I", 0xffffffff) + \
        struct.pack("<B", 1) + \
        "vanilla".encode('utf-8') + b'\0' + \
        "13.4".encode('utf-8') + b'\0'
    s.sendall(struct.pack("<H", len(packet_body) + 2) + packet_body)

    # Receive AI list
    while True:
        print(recv_packet(s))

and it prints the binary/text details of each AI.

But I'm a bit stuck on working out if there are more AIs to come back from the server. Nothing leaps out at me as the total number of AIs, or something that indicates the final AI.

Is there a way of knowing when the client has received the full list of AIs?

[TrueBrain]

Nope.

(I can spend more words on this, but it is the answer to your question :D )

But as you already know what AI you want to fetch (right?), you can also just request the specific AI, and only get that returned. PACKET_CONTENT_CLIENT_INFO_EXTID and friends basically.

[michalc]

Ah... I was about to say that it looks likePACKET_CONTENT_CLIENT_INFO_EXTID can only be used to fetch an AI by its unique ID, not its name. So not quite sure how to get it (/ be sure that it doesn't exist if one is requested that doesn't)

But...

Have now found https://bananas-api.openttd.org/package/ai that gives a way of converting from name to unique ID

Thanks!

[TrueBrain]

And for any content you have seen before, you already know the unique id :) Names can be duplicated, IDs cannot.

[michalc]

Names can be duplicated, IDs cannot.

Oooh... didn't quite realise this...