Steamworks Documentation
Miscellaneous types and functions used by networking APIs.

Describing Network Hosts

Types needed to describe network hosts.

enum ESteamNetworkingIdentityType

Different types of identities that a remote host can have. Most of the time on Steam, this will be a CSteamID. However, in some cases you can disable authentication, in which case a more generic identity will be used.

enum ESteamNetworkingIdentityType { // Dummy/unknown/invalid k_ESteamNetworkingIdentityType_Invalid = 0, // // Basic platform-specific identifiers. // k_ESteamNetworkingIdentityType_SteamID = 16, // 64-bit CSteamID // // Special identifiers. // // Use their IP address (and port) as their "identity". // These types of identities are always unauthenticated. // They are useful for porting plain sockets code, and other // situations where you don't care about authentication. In this // case, the local identity will be "localhost", // and the remote address will be their network address. // // We use the same type for either IPv4 or IPv6, and // the address is always store as IPv6. We use IPv4 // mapped addresses to handle IPv4. k_ESteamNetworkingIdentityType_IPAddress = 1, // Generic string/binary blobs. It's up to your app to interpret this. // This library can tell you if the remote host presented a certificate // signed by somebody you have chosen to trust, with this identity on it. // It's up to you to ultimately decide what this identity means. k_ESteamNetworkingIdentityType_GenericString = 2, k_ESteamNetworkingIdentityType_GenericBytes = 3, // Make sure this enum is stored in an int. k_ESteamNetworkingIdentityType__Force32bit = 0x7fffffff, }}

struct SteamNetworkingIdentity

An abstract way to represent the identity of a network host.

struct SteamNetworkingIdentity { /// Type of identity. ESteamNetworkingIdentityType m_eType; // // Get/Set in various formats. // void Clear(); bool IsInvalid() const; // Return true if we are the invalid type. Does not make any other validity checks (e.g. is SteamID actually valid) void SetSteamID( CSteamID steamID ); CSteamID GetSteamID() const; // Return black CSteamID (!IsValid()) if identity is not a SteamID void SetSteamID64( uint64 steamID ); // Takes SteamID as raw 64-bit number uint64 GetSteamID64() const; // Returns 0 if identity is not SteamID void SetIPAddr( const SteamNetworkingIPAddr &addr ); // Set to specified IP:port const SteamNetworkingIPAddr *GetIPAddr() const; // returns null if we are not an IP address. // "localhost" is equivalent for many purposes to "anonymous." Our remote // will identify us by the network address we use. void SetLocalHost(); // Set to localhost. (We always use IPv6 ::1 for this, not bool IsLocalHost() const; // Return true if this identity is localhost. bool SetGenericString( const char *pszString ); // Returns false if invalid length const char *GetGenericString() const; // Returns nullptr if not generic string type bool SetGenericBytes( const void *data, size_t cbLen ); // Returns false if invalid size. const uint8 *GetGenericBytes( int &cbLen ) const; // Returns null if not generic bytes type /// See if two identities are identical bool operator==(const SteamNetworkingIdentity &x ) const; /// Print to a human-readable string. This is suitable for debug messages /// or any other time you need to encode the identity as a string. It has a /// URL-like format (type:<type-data>). Your buffer should be at least /// k_cchMaxString bytes big to avoid truncation. void ToString( char *buf, size_t cbBuf ) const; /// Parse back a string that was generated using ToString bool ParseString( const char *pszStr ); // Max sizes enum { k_cchMaxString = 128, // Max length of the buffer needed to hold any identity, formatted in string format by ToString k_cchMaxGenericString = 32, // Max length of the string for generic string identities. Including terminating '\0' k_cbMaxGenericBytes = 32, }; // [] };

struct SteamNetworkingIPAddr

Store an IP and port.

IPv6 is always used; IPv4 is represented using "IPv4-mapped" addresses: IPv4 => IPv6 ::ffff:aabb:ccdd. (See RFC 4291 section
struct SteamNetworkingIPAddr { void Clear(); // Set everything to zero. E.g. [::]:0 bool IsIPv6AllZeros() const; // Return true if the IP is ::0. (Doesn't check port.) void SetIPv6( const uint8 *ipv6, uint16 nPort ); // Set IPv6 address. IP is interpreted as bytes, so there are no endian issues. (Same as inaddr_in6.) The IP can be a mapped IPv4 address void SetIPv4( uint32 nIP, uint16 nPort ); // Sets to IPv4 mapped address. IP and port are in host byte order. bool IsIPv4() const; // Return true if IP is mapped IPv4 uint32 GetIPv4() const; // Returns IP in host byte order (e.g. as 0xaabbccdd). Returns 0 if IP is not mapped IPv4. void SetIPv6LocalHost( uint16 nPort = 0); // Set to the IPv6 localhost address ::1, and the specified port. bool IsLocalHost() const; // Return true if this identity is localhost. (Either IPv6 ::1, or IPv4 // Max length of the buffer needed to hold IP formatted using ToString, including '\0' // ([0123:4567:89ab:cdef:0123:4567:89ab:cdef]:12345) enum { k_cchMaxString = 48 }; /// Print to a string, with or without the port. Mapped IPv4 addresses are printed /// as dotted decimal (, otherwise this will print the canonical /// form according to RFC5952. If you include the port, IPv6 will be surrounded by /// brackets, e.g. [::1:2]:80. Your buffer should be at least k_cchMaxString bytes /// to avoid truncation inline void ToString( char *buf, size_t cbBuf, bool bWithPort ) const; /// Parse an IP address and optional port. If a port is not present, it is set to 0. /// (This means that you cannot tell if a zero port was explicitly specified.) inline bool ParseString( const char *pszStr ); union { uint8 m_ipv6[]; struct // IPv4 "mapped address" (rfc4038 section 4.2) { uint64 m_8zeros; uint16 m_0000; uint16 m_ffff; uint8 m_ip[]; // NOTE: As bytes, i.e. network byte order } m_ipv4; }; uint16 m_port; // Host byte order /// See if two addresses are identical bool operator==(const SteamNetworkingIPAddr &x ) const; };

Connection status

These types are used to describe the status of a connection. See ISteamnetworkingSockets::GetConnectionInfo, SteamNetConnectionStatusChangedCallback_t

enum ESteamNetworkingState

Enumerates high level connection states.

enum ESteamNetworkingConnectionState { /// Dummy value used to indicate an error condition in the API. /// Specified connection doesn't exist or has already been closed. k_ESteamNetworkingConnectionState_None = 0, /// We are trying to establish whether peers can talk to each other, /// whether they WANT to talk to each other, perform basic auth, /// and exchange crypt keys. /// /// - For connections on the "client" side (initiated locally): /// We're in the process of trying to establish a connection. /// Depending on the connection type, we might not know who they are. /// Note that it is not possible to tell if we are waiting on the /// network to complete handshake packets, or for the application layer /// to accept the connection. /// /// - For connections on the "server" side (accepted through listen socket): /// We have completed some basic handshake and the client has presented /// some proof of identity. The connection is ready to be accepted /// using AcceptConnection(). /// /// In either case, any unreliable packets sent now are almost certain /// to be dropped. Attempts to receive packets are guaranteed to fail. /// You may send messages if the send mode allows for them to be queued. /// but if you close the connection before the connection is actually /// established, any queued messages will be discarded immediately. /// (We will not attempt to flush the queue and confirm delivery to the /// remote host, which ordinarily happens when a connection is closed.) k_ESteamNetworkingConnectionState_Connecting = 1, /// Some connection types use a back channel or trusted 3rd party /// for earliest communication. If the server accepts the connection, /// then these connections switch into the rendezvous state. During this /// state, we still have not yet established an end-to-end route (through /// the relay network), and so if you send any messages unreliable, they /// are going to be discarded. k_ESteamNetworkingConnectionState_FindingRoute = 2, /// We've received communications from our peer (and we know /// who they are) and are all good. If you close the connection now, /// we will make our best effort to flush out any reliable sent data that /// has not been acknowledged by the peer. (But note that this happens /// from within the application process, so unlike a TCP connection, you are /// not totally handing it off to the operating system to deal with it.) k_ESteamNetworkingConnectionState_Connected = 3, /// Connection has been closed by our peer, but not closed locally. /// The connection still exists from an API perspective. You must close the /// handle to free up resources. If there are any messages in the inbound queue, /// you may retrieve them. Otherwise, nothing may be done with the connection /// except to close it. /// /// This stats is similar to CLOSE_WAIT in the TCP state machine. k_ESteamNetworkingConnectionState_ClosedByPeer = 4, /// A disruption in the connection has been detected locally. (E.g. timeout, /// local internet connection disrupted, etc.) /// /// The connection still exists from an API perspective. You must close the /// handle to free up resources. /// /// Attempts to send further messages will fail. Any remaining received messages /// in the queue are available. k_ESteamNetworkingConnectionState_ProblemDetectedLocally = 5, // // The following values are used internally and will not be returned by any API. // We document them here to provide a little insight into the state machine that is used // under the hood. // /// We've disconnected on our side, and from an API perspective the connection is closed. /// No more data may be sent or received. All reliable data has been flushed, or else /// we've given up and discarded it. We do not yet know for sure that the peer knows /// the connection has been closed, however, so we're just hanging around so that if we do /// get a packet from them, we can send them the appropriate packets so that they can /// know why the connection was closed (and not have to rely on a timeout, which makes /// it appear as if something is wrong). k_ESteamNetworkingConnectionState_FinWait = -1, /// We've disconnected on our side, and from an API perspective the connection is closed. /// No more data may be sent or received. From a network perspective, however, on the wire, /// we have not yet given any indication to the peer that the connection is closed. /// We are in the process of flushing out the last bit of reliable data. Once that is done, /// we will inform the peer that the connection has been closed, and transition to the /// FinWait state. /// /// Note that no indication is given to the remote host that we have closed the connection, /// until the data has been flushed. If the remote host attempts to send us data, we will /// do whatever is necessary to keep the connection alive until it can be closed properly. /// But in fact the data will be discarded, since there is no way for the application to /// read it back. Typically this is not a problem, as application protocols that utilize /// the lingering functionality are designed for the remote host to wait for the response /// before sending any more data. k_ESteamNetworkingConnectionState_Linger = -2, /// Connection is completely inactive and ready to be destroyed k_ESteamNetworkingConnectionState_Dead = -3, k_ESteamNetworkingConnectionState__Force32Bit = 0x7fffffff };

enum ESteamNetConnectionEnd

Enumerate various causes of connection termination. These are designed to work similar to HTTP error codes: the numeric range gives you a rough classification as to the source of the problem.
enum ESteamNetConnectionEnd { // Invalid/sentinel value k_ESteamNetConnectionEnd_Invalid = 0, // // Application codes. These are the values you will pass to // ISteamNetworkingSockets::CloseConnection. You can use these codes if // you want to plumb through application-specific reason codes. If you don't // need this facility, feel free to always pass // k_ESteamNetConnectionEnd_App_Generic. // // The distinction between "normal" and "exceptional" termination is // one you may use if you find useful, but it's not necessary for you // to do so. The only place where we distinguish between normal and // exceptional is in connection analytics. If a significant // proportion of connections terminates in an exceptional manner, // this can trigger an alert. // // 1xxx: Application ended the connection in a "usual" manner. // E.g.: user intentionally disconnected from the server, // gameplay ended normally, etc k_ESteamNetConnectionEnd_App_Min = 1000, k_ESteamNetConnectionEnd_App_Generic = k_ESteamNetConnectionEnd_App_Min, // Use codes in this range for "normal" disconnection k_ESteamNetConnectionEnd_App_Max = 1999, // 2xxx: Application ended the connection in some sort of exceptional // or unusual manner that might indicate a bug or configuration // issue. // k_ESteamNetConnectionEnd_AppException_Min = 2000, k_ESteamNetConnectionEnd_AppException_Generic = k_ESteamNetConnectionEnd_AppException_Min, // Use codes in this range for "unusual" disconnection k_ESteamNetConnectionEnd_AppException_Max = 2999, // // System codes. These will be returned by the system when // the connection state is k_ESteamNetworkingConnectionState_ClosedByPeer // or k_ESteamNetworkingConnectionState_ProblemDetectedLocally. It is // illegal to pass a code in this range to ISteamNetworkingSockets::CloseConnection // // 3xxx: Connection failed or ended because of problem with the // local host or their connection to the Internet. k_ESteamNetConnectionEnd_Local_Min = 3000, // You cannot do what you want to do because you're running in offline mode. k_ESteamNetConnectionEnd_Local_OfflineMode = 3001, // We're having trouble contacting many (perhaps all) relays. // Since it's unlikely that they all went offline at once, the best // explanation is that we have a problem on our end. Note that we don't // bother distinguishing between "many" and "all", because in practice, // it takes time to detect a connection problem, and by the time // the connection has timed out, we might not have been able to // actively probe all of the relay clusters, even if we were able to // contact them at one time. So this code just means that: // // * We don't have any recent successful communication with any relay. // * We have evidence of recent failures to communicate with multiple relays. k_ESteamNetConnectionEnd_Local_ManyRelayConnectivity = 3002, // A hosted server is having trouble talking to the relay // that the client was using, so the problem is most likely // on our end k_ESteamNetConnectionEnd_Local_HostedServerPrimaryRelay = 3003, // We're not able to get the network config. This is // *almost* always a local issue, since the network config // comes from the CDN, which is pretty darn reliable. k_ESteamNetConnectionEnd_Local_NetworkConfig = 3004, // Steam rejected our request because we don't have rights // to do this. k_ESteamNetConnectionEnd_Local_Rights = 3005, k_ESteamNetConnectionEnd_Local_Max = 3999, // 4xxx: Connection failed or ended, and it appears that the // cause does NOT have to do with the local host or their // connection to the Internet. It could be caused by the // remote host, or it could be somewhere in between. k_ESteamNetConnectionEnd_Remote_Min = 4000, // The connection was lost, and as far as we can tell our connection // to relevant services (relays) has not been disrupted. This doesn't // mean that the problem is "their fault", it just means that it doesn't // appear that we are having network issues on our end. k_ESteamNetConnectionEnd_Remote_Timeout = 4001, // Something was invalid with the cert or crypt handshake // info you gave me, I don't understand or like your key types, // etc. k_ESteamNetConnectionEnd_Remote_BadCrypt = 4002, // You presented me with a cert that was I was able to parse // and *technically* we could use encrypted communication. // But there was a problem that prevents me from checking your identity // or ensuring that somebody int he middle can't observe our communication. // E.g.: - the CA key was missing (and I don't accept unsigned certs) // - The CA key isn't one that I trust, // - The cert doesn't was appropriately restricted by app, user, time, data center, etc. // - The cert wasn't issued to you. // - etc k_ESteamNetConnectionEnd_Remote_BadCert = 4003, // We couldn't rendezvous with the remote host because // they aren't logged into Steam k_ESteamNetConnectionEnd_Remote_NotLoggedIn = 4004, // We couldn't rendezvous with the remote host because // they aren't running the right application. k_ESteamNetConnectionEnd_Remote_NotRunningApp = 4005, // Something wrong with the protocol version you are using. // (Probably the code you are running is too old.) k_ESteamNetConnectionEnd_Remote_BadProtocolVersion = 4006, k_ESteamNetConnectionEnd_Remote_Max = 4999, // 5xxx: Connection failed for some other reason. k_ESteamNetConnectionEnd_Misc_Min = 5000, // A failure that isn't necessarily the result of a software bug, // but that should happen rarely enough that it isn't worth specifically // writing UI or making a localized message for. // The debug string should contain further details. k_ESteamNetConnectionEnd_Misc_Generic = 5001, // Generic failure that is most likely a software bug. k_ESteamNetConnectionEnd_Misc_InternalError = 5002, // The connection to the remote host timed out, but we // don't know if the problem is on our end, in the middle, // or on their end. k_ESteamNetConnectionEnd_Misc_Timeout = 5003, // We're having trouble talking to the relevant relay. // We don't have enough information to say whether the // problem is on our end or not. k_ESteamNetConnectionEnd_Misc_RelayConnectivity = 5004, // There's some trouble talking to Steam. k_ESteamNetConnectionEnd_Misc_SteamConnectivity = 5005, // A server in a dedicated hosting situation has no relay sessions // active with which to talk back to a client. (It's the client's // job to open and maintain those sessions.) k_ESteamNetConnectionEnd_Misc_NoRelaySessionsToClient = 5006, k_ESteamNetConnectionEnd_Misc_Max = 5999, };


Describe the state of a connection.
struct SteamNetConnectionInfo_t { /// Who is on the other end? Depending on the connection type and phase of the connection, we might not know SteamNetworkingIdentity m_identityRemote; /// Arbitrary user data set by the local application code int64 m_nUserData; /// Handle to listen socket this was connected on, or k_HSteamListenSocket_Invalid if we initiated the connection HSteamListenSocket m_hListenSocket; /// Remote address. Might be all 0's if we don't know it, or if this is N/A. /// (E.g. Basically everything except direct UDP connection.) SteamNetworkingIPAddr m_addrRemote; uint16 m__pad1; /// What data center is the remote host in? (0 if we don't know.) SteamNetworkingPOPID m_idPOPRemote; /// What relay are we using to communicate with the remote host? /// (0 if not applicable.) SteamNetworkingPOPID m_idPOPRelay; /// High level state of the connection ESteamNetworkingConnectionState m_eState; /// Basic cause of the connection termination or problem. /// See ESteamNetConnectionEnd for the values used int m_eEndReason; /// Human-readable, but non-localized explanation for connection /// termination or problem. This is intended for debugging / /// diagnostic purposes only, not to display to users. It might /// have some details specific to the issue. char m_szEndDebug[]; /// Debug description. This includes the connection handle, /// connection type (and peer information), and the app name. /// This string is used in various internal logging messages char m_szConnectionDescription[]; /// Internal stuff, room to change API easily uint32 reserved[64]; };


Quick connection state, pared down to something you could call more frequently without it being too big of a perf hit.

struct SteamNetworkingQuickConnectionStatus { /// High level state of the connection ESteamNetworkingConnectionState m_eState; /// Current ping (ms) int m_nPing; /// Connection quality measured locally, 0...1. (Percentage of packets delivered /// end-to-end in order). float m_flConnectionQualityLocal; /// Packet delivery success rate as observed from remote host float m_flConnectionQualityRemote; /// Current data rates from recent history. float m_flOutPacketsPerSec; float m_flOutBytesPerSec; float m_flInPacketsPerSec; float m_flInBytesPerSec; /// Estimate rate that we believe that we can send data to our peer. /// Note that this could be significantly higher than m_flOutBytesPerSec, /// meaning the capacity of the channel is higher than you are sending data. /// (That's OK!) int m_nSendRateBytesPerSecond; /// Number of bytes pending to be sent. This is data that you have recently /// requested to be sent but has not yet actually been put on the wire. The /// reliable number ALSO includes data that was previously placed on the wire, /// but has now been scheduled for re-transmission. Thus, it's possible to /// observe m_cbPendingReliable increasing between two checks, even if no /// calls were made to send reliable data between the checks. Data that is /// awaiting the Nagle delay will appear in these numbers. int m_cbPendingUnreliable; int m_cbPendingReliable; /// Number of bytes of reliable data that has been placed the wire, but /// for which we have not yet received an acknowledgment, and thus we may /// have to re-transmit. int m_cbSentUnackedReliable; /// If you asked us to send a message right now, how long would that message /// sit in the queue before we actually started putting packets on the wire? /// (And assuming Nagle does not cause any packets to be delayed.) /// /// In general, data that is sent by the application is limited by the /// bandwidth of the channel. If you send data faster than this, it must /// be queued and put on the wire at a metered rate. Even sending a small amount /// of data (e.g. a few MTU, say ~3k) will require some of the data to be delayed /// a bit. /// /// In general, the estimated delay will be approximately equal to /// /// ( m_cbPendingUnreliable+m_cbPendingReliable ) / m_nSendRateBytesPerSecond /// /// plus or minus one MTU. It depends on how much time has elapsed since the last /// packet was put on the wire. For example, the queue might have *just* been emptied, /// and the last packet placed on the wire, and we are exactly up against the send /// rate limit. In that case we might need to wait for one packet's worth of time to /// elapse before we can send again. On the other extreme, the queue might have data /// in it waiting for Nagle. (This will always be less than one packet, because as soon /// as we have a complete packet we would send it.) In that case, we might be ready /// to send data now, and this value will be 0. SteamNetworkingMicroseconds m_usecQueueTime; };

Network messages

const int k_cbMaxSteamNetworkingSocketsMessageSizeSend = 512 * 1024;
Max size of a single message that we can SEND.
Note: We might be wiling to receive larger messages, and our peer might, too.


A message that has been received
struct SteamNetworkingMessage_t { /// Message payload void *m_pData; /// Size of the payload. int m_cbSize; /// For messages received on connections: what connection did this come from? /// For outgoing messages: what connection to send it to? /// Not used when using the ISteamNetworkingMessages interface HSteamNetConnection m_conn; /// For inbound messages: Who sent this to us? /// For outbound messages on connections: not used. /// For outbound messages on the ad-hoc ISteamNetworkingMessages interface: who should we send this to? SteamNetworkingIdentity m_identityPeer; /// For messages received on connections, this is the user data /// associated with the connection. /// /// This is *usually* the same as calling GetConnection() and then /// fetching the user data associated with that connection, but for /// the following subtle differences: /// /// - This user data will match the connection's user data at the time /// is captured at the time the message is returned by the API. /// If you subsequently change the userdata on the connection, /// this won't be updated. /// - This is an inline call, so it's *much* faster. /// - You might have closed the connection, so fetching the user data /// would not be possible. /// /// Not used when sending messages, int64 m_nConnUserData; /// Local timestamp when the message was received /// Not used for outbound messages. SteamNetworkingMicroseconds m_usecTimeReceived; /// Message number assigned by the sender. /// This is not used for outbound messages int64 m_nMessageNumber; /// Function used to free up m_pData. This mechanism exists so that /// apps can create messages with buffers allocated from their own /// heap, and pass them into the library. This function will /// usually be something like: /// /// free( pMsg->m_pData ); void (*m_pfnFreeData)( SteamNetworkingMessage_t *pMsg ); /// Function to used to decrement the internal reference count and, if /// it's zero, release the message. You should not set this function pointer, /// or need to access this directly! Use the Release() function instead! void (*m_pfnRelease)( SteamNetworkingMessage_t *pMsg ); /// When using ISteamNetworkingMessages, the channel number the message was received on /// (Not used for messages sent or received on "connections") int m_nChannel; /// Bitmask of k_nSteamNetworkingSend_xxx flags. /// For received messages, only the k_nSteamNetworkingSend_Reliable bit is valid. /// For outbound messages, all bits are relevant int m_nFlags; /// Arbitrary user data that you can use when sending messages using /// ISteamNetworkingUtils::AllocateMessage and ISteamNetworkingSockets::SendMessage. /// (The callback you set in m_pfnFreeData might use this field.) /// /// Not used for received messages. int64 m_nUserData; /// You MUST call this when you're done with the object, /// to free up memory, etc. inline void Release(); };

Flags used for message sending

These values are used in bitmask parameters to functions such as ISteamNetworkingSockets::SendMessageToConnection

const int k_nSteamNetworkingSend_Unreliable = 0;
Send the message unreliably. Can be lost. Messages *can* be larger than a single MTU (UDP packet), but there is no retransmission, so if any piece of the message is lost, the entire message will be dropped.

The sending API does have some knowledge of the underlying connection, so if there is no NAT-traversal accomplished or there is a recognized adjustment happening on the connection, the packet will be batched until the connection is open again.

Migration note: This is not exactly the same as k_EP2PSendUnreliable! You probably want k_ESteamNetworkingSendType_UnreliableNoNagle

const int k_nSteamNetworkingSend_NoNagle = 1;
Disable Nagle's algorithm.

By default, Nagle's algorithm is applied to all outbound messages. This means that the message will NOT be sent immediately, in case further messages are sent soon after you send this, which can be grouped together. Any time there is enough buffered data to fill a packet, the packets will be pushed out immediately, but partially-full packets not be sent until the Nagle timer expires. See ISteamNetworkingSockets::FlushMessagesOnConnection, ISteamNetworkingMessages::FlushMessagesToUser

NOTE: Don't just send every message without Nagle because you want packets to "get there quicker". Make sure you understand the problem that Nagle is solving before disabling it. If you are sending small messages, often many at the same time, then it is very likely that it will be more efficient to leave Nagle enabled. A typical proper use of this flag is when you are sending what you know will be the last message sent for a while (e.g. the last in the server simulation tick to a particular client), and you use this flag to flush all messages.

const int k_nSteamNetworkingSend_UnreliableNoNagle = k_nSteamNetworkingSend_Unreliable|k_nSteamNetworkingSend_NoNagle;
Send a message unreliably, bypassing Nagle's algorithm for this message and any messages currently pending on the Nagle timer. This is equivalent to using steamnetworkingtypes::k_ESteamNetworkingSend_Unreliable and then immediately flushing the messages using ISteamNetworkingSockets::FlushMessagesOnConnection or ISteamNetworkingMessages::FlushMessagesToUser. (But using this flag is more efficient since you only make one API call.)

const int k_nSteamNetworkingSend_NoDelay = 4;
If the message cannot be sent very soon (because the connection is still doing some initial handshaking, route negotiations, etc), then just drop it. This is only applicable for unreliable messages. Using this flag on reliable messages is invalid.

const int k_nSteamNetworkingSend_UnreliableNoDelay = k_nSteamNetworkingSend_Unreliable|k_nSteamNetworkingSend_NoDelay|k_nSteamNetworkingSend_NoNagle;
Send an unreliable message, but if it cannot be sent relatively quickly, just drop it instead of queuing it. This is useful for messages that are not useful if they are excessively delayed, such as voice data.

A message will be dropped under the following circumstances:
  • the connection is not fully connected. (E.g. the "Connecting" or "FindingRoute" states)
  • there is a sufficiently large number of messages queued up already such that the current messagewill not be placed on the wire in the next ~200ms or so.

If a message is dropped for these reasons, k_EResultIgnored will be returned.

NOTE: The Nagle algorithm is not used, and if the message is not dropped, any messages waiting on the Nagle timer are immediately flushed.

const int k_nSteamNetworkingSend_Reliable = 8;
Reliable message send. Can send up to k_cbMaxSteamNetworkingSocketsMessageSizeSend bytes in a single message. Does fragmentation/re-assembly of messages under the hood, as well as a sliding window for efficient sends of large chunks of data.

The Nagle algorithm is used. See notes on k_ESteamNetworkingSendType_Unreliable for more details. See k_ESteamNetworkingSendType_ReliableNoNagle, ISteamNetworkingSockets::FlushMessagesOnConnection, ISteamNetworkingMessages::FlushMessagesToUser

Migration note: This is NOT the same as k_EP2PSendReliable, it's more like k_EP2PSendReliableWithBuffering

const int k_nSteamNetworkingSend_ReliableNoNagle = k_nSteamNetworkingSend_Reliable|k_nSteamNetworkingSend_NoNagle;
Send a message reliably, but bypass Nagle's algorithm.

Migration note: This is equivalent to k_EP2PSendReliable

Ping location / measurement

ISteamNetworkingutils has functions for estimating the ping time between two Internet hosts without sending any packets.


struct SteamNetworkPingLocation_t { uint8 m_data[]; }
Opaque object that describes a "location" on the Internet with sufficient detail that we can reasonably estimate an upper bound on the ping between the two hosts, even if a direct route between the hosts is not possible, and the connection must be routed through the Steam Datagram Relay network.

This does not contain any information that identifies the host. Indeed, if two hosts are in the same building or otherwise have nearly identical networking characteristics, then it's valid to use the same location object for both of them.

NOTE: This object should only be used in the same process! Do not serialize it, send it over the wire, or persist it in a file or database! If you need to do that, convert it to a string representation using the methods in ISteamNetworkingUtils


const int k_cchMaxSteamNetworkingPingLocationString = 1024;
Max possible length of a ping location, in string format. This is an extremely conservative worst case value which leaves room for future syntax enhancements. Most strings in practice are a lot shorter. If you are storing many of these, you will very likely benefit from using dynamic memory.


You can control different operating parameters, on a global or connection-specific basis. The methdos to do this are in ISteamNetworkingUtils


Configuration values can be applied to different types of objects.
enum ESteamNetworkingConfigScope { /// Get/set global option, or defaults. Even options that apply to more specific scopes /// have global scope, and you may be able to just change the global defaults. If you /// need different settings per connection (for example), then you will need to set those /// options at the more specific scope. k_ESteamNetworkingConfig_Global = 1, /// Some options are specific to a particular interface. Note that all connection /// and listen socket settings can also be set at the interface level, and they will /// apply to objects created through those interfaces. k_ESteamNetworkingConfig_SocketsInterface = 2, /// Options for a listen socket. Listen socket options can be set at the interface layer, /// if you have multiple listen sockets and they all use the same options. /// You can also set connection options on a listen socket, and they set the defaults /// for all connections accepted through this listen socket. (They will be used if you don't /// set a connection option.) k_ESteamNetworkingConfig_ListenSocket = 3, /// Options for a specific connection. k_ESteamNetworkingConfig_Connection = 4, };


Different configuration values have different data types
enum ESteamNetworkingConfigDataType { k_ESteamNetworkingConfig_Int32 = 1, k_ESteamNetworkingConfig_Int64 = 2, k_ESteamNetworkingConfig_Float = 3, k_ESteamNetworkingConfig_String = 4, k_ESteamNetworkingConfig_FunctionPtr = 5, // NOTE: When setting callbacks, you should put the pointer into a variable and pass a pointer to that variable. };


Configuration options
enum ESteamNetworkingConfigValue { k_ESteamNetworkingConfig_Invalid = 0, /// [global float, 0--100] Randomly discard N pct of packets instead of sending/recv /// This is a global option only, since it is applied at a low level /// where we don't have much context k_ESteamNetworkingConfig_FakePacketLoss_Send = 2, k_ESteamNetworkingConfig_FakePacketLoss_Recv = 3, /// [global int32]. Delay all outbound/inbound packets by N ms k_ESteamNetworkingConfig_FakePacketLag_Send = 4, k_ESteamNetworkingConfig_FakePacketLag_Recv = 5, /// [global float] 0-100 Percentage of packets we will add additional delay /// to (causing them to be reordered) k_ESteamNetworkingConfig_FakePacketReorder_Send = 6, k_ESteamNetworkingConfig_FakePacketReorder_Recv = 7, /// [global int32] Extra delay, in ms, to apply to reordered packets. k_ESteamNetworkingConfig_FakePacketReorder_Time = 8, /// [global float 0--100] Globally duplicate some percentage of packets we send k_ESteamNetworkingConfig_FakePacketDup_Send = 26, k_ESteamNetworkingConfig_FakePacketDup_Recv = 27, /// [global int32] Amount of delay, in ms, to delay duplicated packets. /// (We chose a random delay between 0 and this value) k_ESteamNetworkingConfig_FakePacketDup_TimeMax = 28, /// [connection int32] Timeout value (in ms) to use when first connecting k_ESteamNetworkingConfig_TimeoutInitial = 24, /// [connection int32] Timeout value (in ms) to use after connection is established k_ESteamNetworkingConfig_TimeoutConnected = 25, /// [connection int32] Upper limit of buffered pending bytes to be sent, /// if this is reached SendMessage will return k_EResultLimitExceeded /// Default is 512k (524288 bytes) k_ESteamNetworkingConfig_SendBufferSize = 9, /// [connection int32] Minimum/maximum send rate clamp, 0 is no limit. /// This value will control the min/max allowed sending rate that /// bandwidth estimation is allowed to reach. Default is 0 (no-limit) k_ESteamNetworkingConfig_SendRateMin = 10, k_ESteamNetworkingConfig_SendRateMax = 11, /// [connection int32] Nagle time, in microseconds. When SendMessage is called, if /// the outgoing message is less than the size of the MTU, it will be /// queued for a delay equal to the Nagle timer value. This is to ensure /// that if the application sends several small messages rapidly, they are /// coalesced into a single packet. /// See historical RFC 896. Value is in microseconds. /// Default is 5000us (5ms). k_ESteamNetworkingConfig_NagleTime = 12, /// [connection int32] Don't automatically fail IP connections that don't have /// strong auth. On clients, this means we will attempt the connection even if /// we don't know our identity or can't get a cert. On the server, it means that /// we won't automatically reject a connection due to a failure to authenticate. /// (You can examine the incoming connection and decide whether to accept it.) k_ESteamNetworkingConfig_IP_AllowWithoutAuth = 23, // // Settings for SDR relayed connections // /// [int32 global] If the first N pings to a port all fail, mark that port as unavailable for /// a while, and try a different one. Some ISPs and routers may drop the first /// packet, so setting this to 1 may greatly disrupt communications. k_ESteamNetworkingConfig_SDRClient_ConsecutitivePingTimeoutsFailInitial = 19, /// [int32 global] If N consecutive pings to a port fail, after having received successful /// communication, mark that port as unavailable for a while, and try a /// different one. k_ESteamNetworkingConfig_SDRClient_ConsecutitivePingTimeoutsFail = 20, /// [int32 global] Minimum number of lifetime pings we need to send, before we think our estimate /// is solid. The first ping to each cluster is very often delayed because of NAT, /// routers not having the best route, etc. Until we've sent a sufficient number /// of pings, our estimate is often inaccurate. Keep pinging until we get this /// many pings. k_ESteamNetworkingConfig_SDRClient_MinPingsBeforePingAccurate = 21, /// [int32 global] Set all steam datagram traffic to originate from the same /// local port. By default, we open up a new UDP socket (on a different local /// port) for each relay. This is slightly less optimal, but it works around /// some routers that don't implement NAT properly. If you have intermittent /// problems talking to relays that might be NAT related, try toggling /// this flag k_ESteamNetworkingConfig_SDRClient_SingleSocket = 22, /// [global string] Code of relay cluster to force use. If not empty, we will /// only use relays in that cluster. E.g. 'iad' k_ESteamNetworkingConfig_SDRClient_ForceRelayCluster = 29, /// [connection string] For debugging, generate our own (unsigned) ticket, using /// the specified gameserver address. Router must be configured to accept unsigned /// tickets. k_ESteamNetworkingConfig_SDRClient_DebugTicketAddress = 30, /// [global string] For debugging. Override list of relays from the config with /// this set (maybe just one). Comma-separated list. k_ESteamNetworkingConfig_SDRClient_ForceProxyAddr = 31, // // Log levels for debuging information. A higher priority // (lower numeric value) will cause more stuff to be printed. // k_ESteamNetworkingConfig_LogLevel_AckRTT = 13, // [connection int32] RTT calculations for inline pings and replies k_ESteamNetworkingConfig_LogLevel_PacketDecode = 14, // [connection int32] log SNP packets send k_ESteamNetworkingConfig_LogLevel_Message = 15, // [connection int32] log each message send/recv k_ESteamNetworkingConfig_LogLevel_PacketGaps = 16, // [connection int32] dropped packets k_ESteamNetworkingConfig_LogLevel_P2PRendezvous = 17, // [connection int32] P2P rendezvous messages k_ESteamNetworkingConfig_LogLevel_SDRRelayPings = 18, // [global int32] Ping relays };


Return value of ISteamNetworkintgUtils::GetConfigValue
enum ESteamNetworkingGetConfigValueResult { k_ESteamNetworkingGetConfigValue_BadValue = -1, // No such configuration value k_ESteamNetworkingGetConfigValue_BadScopeObj = -2, // Bad connection handle, etc k_ESteamNetworkingGetConfigValue_BufferTooSmall = -3, // Couldn't fit the result in your buffer k_ESteamNetworkingGetConfigValue_OK = 1, k_ESteamNetworkingGetConfigValue_OKInherited = 2, // A value was not set at this level, but the effective (inherited) value was returned. k_ESteamNetworkingGetConfigValueResult__Force32Bit = 0x7fffffff };


In a few places we need to set configuration options on listen sockets and connections, and have them take effect before the listen socket or connection really starts doing anything. Creating the object and then setting the options "immediately" after creation doesn't work completely, because network packets could be received between the time the object is created and when the options are applied. To set options at creation time in a reliable way, they must be passed to the creation function. This structure is used to pass those options.

For the meaning of these fields, see ISteamNetworkingUtils::SetConfigValue. Basically when the object is created, we just iterate over the list of options and call ISteamNetworkingUtils::SetConfigValueStruct, where the scope arguments are supplied by the object being created.
struct SteamNetworkingConfigValue_t { /// Which option is being set ESteamNetworkingConfigValue m_eValue; /// Which field below did you fill in? ESteamNetworkingConfigDataType m_eDataType; /// Option value union { int32_t m_int32; int64_t m_int64; float m_float; const char *m_string; // Points to your '\0'-terminated buffer void *m_functionPtr; } m_val; };

Valve data centers

Used to describe the topology of the Valve network, identify data centers, etc.

typedef uint32 SteamNetworkingPOPID;
Identifier used for a network location point of presence. (E.g. a Valve data center.)
Typically you won't need to directly manipulate these.

SteamNetworkingPOPID CalculateSteamNetworkingPOPIDFromString( const char *pszCode )
Convert 3- or 4-character ID to 32-bit int.

template <int N> inline void GetSteamNetworkingLocationPOPStringFromID( SteamNetworkingPOPID id, char (&szCode)[N] )
Unpack integer to string representation, including terminating '\0'. Your string should be at least 5 bytes large. (It will fail to compile if this is not the case.)