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include(navbar.html.m4)
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TITLE(Layer one: protocol abstraction)
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Skip this layer if you really want to use Armagetron's networking system
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fast; it contains details you do not need to know from the start.
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This layer is responsible for sending raw data packets to other computers.
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The files <CODE>net_anet.h,net_sysdep.C,net_udp.C</CODE> and
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<CODE>net_wins.C</CODE> are responsible for it;
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they are written in pure C.
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<CODE>net_anet.h</CODE> is the header file with the declarations visible to
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layer two, and <CODE>net_systep.C</CODE> just includes the real
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implementation from <CODE>net_udp.C</CODE> or <CODE>net_wins.C</CODE> depending
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on the system Armagetron is compiled for.
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SECTION(Data structures)
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CODEITEM(sockaddr,struct sockaddr:,
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[Everything the network protocol needs to identify
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a connection to another computer. In the case of UDP, it contains the IP
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address and port number.])
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CODEITEM(socket,Sockets:,
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[represented by integers: in analogy to file descriptors,
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all network IO is done
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through sockets. Every client has one socket where all the messages to/from
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the server are sent/received through. The server has one listening socket for
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the messages from new clients, and one IO socket for each client.
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(With the UDP protocol, all these sockets are really identical, as there is
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no such thing as a connection and no need/possibility to assign a connection
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SECTION(Function list)
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(only the functions layer two actually uses are mentioned)
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CODEITEM(init,Socket ANET_Init();,[Initialises the network system, returns the
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control socket. All future IO is done through that socket.])
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CODEITEM(shutdown,void ANET_Shutdown (void);,Closes the network system.)
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CODEITEM(listen,void ANET_Listen(bool state);,[If state is true, the listening
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socket is initialised (listening at the port ]<CODE>net_hostport=4532</CODE>[)
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and can be queried by]
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<CODE>ANET_CheckNewConnections</CODE>.)
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CODEITEM(checknewconnections,Socket ANET_CheckNewConnections (void);,
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[On the server, this checks if there are any new connections
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from clients wanting to join the game. Returns a socket ready to receive
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the newcomer if there is one, or -1 if not. In case of the UDP protocol,
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even the messages from the known clients are caught by this function
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(as there is no way to distinguish new and old connections with UDP), so layer
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two needs to do some extra checks with this function.
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CODEITEM(getaddrfromname,[int ANET_GetAddrFromName
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(const char *name, struct sockaddr *addr);],[
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Fills <CODE>*addr</CODE> with the information necessary to reach the server
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<CODE>name</CODE> (containing the IP address in numerical notation or the
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the port number is set to ]<CODE>net_hostport=4532</CODE> to match the port
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the server listens on.)
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CODEITEM(connect,ANET_Connect(Socket s,struct sockaddr *addr);,[
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Opens a connection to the computer given by ]<CODE>addr</CODE>[ through
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the socket] <CODE>s</CODE>.
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[As UDP is a connectionless protocol, this does not do
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CODEITEM(write,int ANET_Write (Socket sock, const byte *buf, int len, struct sockaddr *addr);,
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Sends <CODE>len</CODE> bytes of data from <CODE>buf</CODE> through the socket
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<CODE>sock</CODE> to the peer identified with <CODE>*addr</CODE>. A connection
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has to be established before with <CODE>ANET_Connect()</CODE>.)
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CODEITEM(read,int ANET_Read (Socket sock, byte *buf, int len, struct sockaddr *addr);,
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Reads up to <CODE>len</CODE> bytes from the connection associated to
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socket <CODE>sock</CODE> and stores them in the buffer <CODE>buf</CODE>.
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[(If a connectionless protocol like UDP is used and the socket is a listening
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socket, this can mean ANY data coming in at the port the socket listens on...)
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]The sender's address is stored in <CODE>*addr</CODE>[, the number of actually
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read bytes is returned (Zero means no data was received.)])
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CODEITEM(addrtostring,char *ANET_AddrToString (const struct sockaddr *addr);,[
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Returns the information from ]<CODE>addr</CODE>[ in human readable form.])
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CODEITEM(addrcompare,int ANET_AddrCompare (struct sockaddr *addr1, struct sockaddr *addr2);,
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Checks whether <CODE>*addr1</CODE> and <CODE>*addr2</CODE> [are the same
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computer (ignoring the port number). If they are, 0 is returned, -1 if not.])
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CODEITEM(getsocketport,int ANET_GetSocketPort (struct sockaddr *addr),
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Returns the port number from <CODE>*addr</CODE>.)
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