Connecting to other systems

Find who to connect to There are 4 ways to find other systems to connect to: Direct IP entry (you already know it) LAN Broadcast Using the lightweight database plugin as a directory server Using the lobby server Option 1: Direct IP Entry The simplest and easiest way from a coding perspective is to either hardcode an IP address or domain name, or present a GUI to the user asking them to enter the IP address of the other system they would like to connect to. Most of the samples use this method. Back when networked games first came out, this was the only option provided. Advantages: Little to no GUI work required of programmers and artists If the IP address or domain name is fixed, such as if you are running a dedicated server, this is the correct solution Disadvantages: Inflexible Users will only be able to play with people they already know. Note: Use 127.0.0.1, or localhost, to connect to another instance of RakPeer on the same computer, or the same application. Option 2: Lan Broadcast RakNet supports the ability to broadcast a packet to find other systems on a local LAN, with optional data to send and retrieve identifying the application. The sample LANServerDiscovery demonstrates this technique. In RakPeerInterface.h, the Ping function will can do this, as follows rakPeer->Ping("255.255.255.255", REMOTE_GAME_PORT, onlyReplyOnAcceptingConnections); REMOTE_GAME_PORT should be whatever port the other system is running the application you care about on. onlyReplyOnAcceptingConnections is a boolean indicating if the other system should reply, even if they have no connections available for you to connect to. Open systems will reply with ID_PONG. From the sample: if (p->data[0]==ID_PONG) { RakNetTime time; memcpy((char*)&time, p->data+1, sizeof(RakNetTime)); printf("Got pong from %s with time %i\n", p->systemAddress.ToString(), RakNet::GetTime() - time); } In order to send custom user data, call RakPeer::SetOfflinePingResponse(customUserData, lengthInBytes); RakNet will copy the data passed to it and return this data appended to ID_PONG. Extending the example above to read custom user data: if (p->data[0]==ID_PONG) { RakNetTime time; memcpy((char*)&time, p->data+1, sizeof(RakNetTime)); memcpy(customUserData, p->data+1+sizeof(RakNetTime), p->length-1-sizeof(RakNetTime)); The +1 and -1 is the one byte ID_PONG. Note: there is a hardcoded define MAX_OFFLINE_DATA_LENGTH in RakPeer.cpp limiting the length of your custom user data. Change this value and recompile if your data is larger than this define. Advantages: You can join games automatically on program startup, no GUI or user interaction required Best way to find games on the LAN Disadvantages: Won't work for the general internet Not as flexible as the lightweight database plugin Option 3: Lightweight Database Plugin The lightweight database plugin provides functionality to add, remove, update, and query rows in one or more table(s) hosted on another system. While you could use it for any purpose, the design and intent behind the class was to allow one system to act as a directory server, listing games for clients to connect to. This plugin provides functionality similar to the game listings you find on online services, or for first person shooters. See the sample LightweightDatabase for an example of how to use this plugin. Advantages: Very flexible, can support any number of fields or datatypes Easy to find servers Automatically pings servers, and drops them off the list if they crash. Disadvantages: Requires a separate, dedicated server to host the plugin Does not support persistent data, such as friends. Option 4: Lobby Server The lobby server provides a database driven service for players to interact and start games. It provides features such as friends, matchmaking, emails, ranking, instant messenging, quick match, rooms, and room moderation. See the samples LobbyServerTest and LobbyClientTest for a demonstration of how to use this feature. Advantages: The most flexible solution for players to join games Allows users to interact before starting games Builds community Supports multiple titles Disadvantages: Requires a separate, dedicated server to host the plugin, and the server must have database support Feature is relatively large and complex compared to a simple game listing, requiring a good investment in time and programming Initiate connection attempt Once you know the IP address of the remote system(s) to connect to, use RakPeerInterface::Connect() to initiate an asynchronous connection attempt. The parameters to connect are: bool Connect( const char* host, unsigned short remotePort, const char *passwordData, int passwordDataLength, unsigned connectionSocketIndex=0 ); host is an IP address, or domain name. remotePort is the port that the remote system is listening on, which you passed to the Startup() function passwordData is optional binary data to send with the connection request. If this data does not match what was passed to RakPeerInterface::SetPassword(), the remote system will reply with ID_INVALID_PASSWORD. passwordDataLength is the length, in bytes, of passwordData connectionSocketIndex is which socket to use should RakNet be bound to more than one socket. This can be ignored by most users (use the default parameter 0). See RakPeer::Startup() in the header file RakPeerInterface.h for more information on this parameter. Connect() will return true for a successful attempt, false if you are already connected to this system, or if the domain name cannot be resolved. Note: Connect() returning true does NOT mean you are connected. It means you should wait for the message ID_CONNECTION_REQUEST_ACCEPTED or ID_CONNECTION_ATTEMPT_FAILED. In the meantime, your GUI should show a waiting screen. Troubleshooting connection failure If ID_CONNECTION_ATTEMPT_FAILED is returned, this means you could not connect to that system. Possible reasons include: The IP address is wrong That system is not running RakNet, or RakPeerInterface::Startup() was not called The remote system has started RakNet, but RakPeerInterface::SetMaximumIncomingConnections() was not called A firewall on either system is blocking UDP packets on the port you have chosen A router on the remote system is blocking incoming UDP packets on the port you have chosen. See the NAT Punchthrough plugin to resolve this. On Windows Vista, the network driver security service pack sometimes breaks UDP, not just for RakNet, but in general, even for DirectPlay. This service pack should be rolled back, and not installed. (This may be fixed eventually) Secure connections are enabled, and your system failed the security check. Your IP address was banned with RakPeerInterface::AddToBanList(). Note that some plugins, such as the connection filter, have the option to ban IP addresses automatically. Assuming you are able to connect, it is time to go onto the section: Creating Packets

See Also

Index Connection Filter Creating Packets Lightweight Database plugin NAT Punchthrough plugin Secure connections FAQ