The Invisible Internet Client Protocol (I2CP) allows applications simplified access to the I2P network without requiring them to deal with the issues involved with the Invisible Internet Network Protocol (I2NP). Specifically, it defines the wire level protocol as well as semantics for the messages passed between clients and the router for communicating with the router over bidirectional TCP/IP sockets. I2CP does not specify how the client libraries are created, what APIs they expose to applications, or even what language they're written in.
I2CP requires that the client can access the router over bidirectional TCP sockets. In nearly all cases, these connections will be over to the local machine.
I2CP does not provide data confidentiality or handle lossy connections beyond what TCP has built in. For this reason, I2CP really should only be run between clients and routers on the same machine or over trusted networks. Secured I2CP transports may be added in the future. I2CP however does not expose any private keys across the wire - proof of authorization to collect messages for a Destination is provided by public key signatures.
These classes are the currently defined messages in the Invisible Internet Client Protocol (I2CP), though common data structures are located in the I2P Common Data Structure Specification. For simplicity, all I2CP messages begin with the same structure, though that structure is not listed below. Specifically, all I2CP messages transmitted begin with a 4 byte Integer specifying the entire size of the current message's body (the body being what's specified below), followed by a 1 byte Integer specifying the type of message (the id field below), after which the rest of the message is formatted according to the type of message, as specified below.
If there is a fatal error causing either the client or the router to desire to cancel sending a message part way through, it should drop its connection. Administrative sessions are not stateful (aka each administrative message from client to router must provide authentication), but normal client sessions are stateful and survive disconnects. Client sessions expire when either the client sends a DestroySessionMessage or the router times out the session according to its own configurable timer. If a client sends any message other than a CreateSessionMessage when there is no valid session, the router must reply with a SessionStatusMessage specifying that the session is not valid.
Note: the contents and bitbuckets for specific DataStructures are detailed in the I2P Data Structures Spec.
Interface Summary Interface Description I2CPMessageDefines the base functionality of API messages As of 0.9.48, does NOT extend DataStructure. I2CPMessageReader.I2CPMessageEventListenerDefines the different events the reader produces while reading the stream
Class Summary Class Description AbuseReasonDefines the structure for why abuse was reported either by the client to the router or by the router to the client AbuseSeverityProvides a severity level (larger numbers are more severe) in association with a client reporting abusive behavior to the router or the router reporting it to the client BandwidthLimitsMessageTell the other side the limits BlindingInfoMessageAdvise the router that the endpoint is blinded. CreateLeaseSet2MessageLike CreateLeaseSetMessage, but supports both old and new LeaseSet types, including LS2, Meta, and Encrypted. CreateLeaseSetMessageDefines the message a client sends to a router when authorizing the LeaseSet CreateSessionMessageDefines the message a client sends to a router when establishing a new session. DestLookupMessageRequest the router look up the dest for a hash DestReplyMessageResponse to DestLookupMessage. DestroySessionMessageDefines the message a client sends to a router when destroying existing session. DisconnectMessageDefines the message a client sends to a router when destroying existing session. GetBandwidthLimitsMessageRequest the router tells us the current bw limits GetDateMessageRequest the other side to send us what they think the current time is. HostLookupMessageRequest the router look up the dest for a hash or a host. HostReplyMessageResponse to HostLookupMessage. I2CPMessageHandlerHandle messages from the server for the client or vice versa I2CPMessageImplDefines the base message implementation. I2CPMessageReaderThe I2CPMessageReader reads an InputStream (using
I2CPMessageHandler) and passes out events to a registered listener, where events are either messages being received, exceptions being thrown, or the connection being closed.
MessageIdDefines the message ID of a message delivered between a router and a client in a particular session. MessagePayloadMessageDefines the payload message a router sends to the client MessageStatusMessageDefines the message a router sends to a client about a single message. ReceiveMessageBeginMessageDefines the message a client sends to a router when asking the router to start sending a message to it. ReceiveMessageEndMessageDefines the message a client sends to a router when asking the router to start sending a message to it. ReconfigureSessionMessageDefines the message a client sends to a router when updating the config on an existing session. ReportAbuseMessageDefines the message a client sends to a router when asking the router what its address visibility is RequestLeaseSetMessageDefines the message a router sends to a client to request that a leaseset be created and signed. RequestVariableLeaseSetMessageDefines the message a router sends to a client to request that a leaseset be created and signed. SendMessageExpiresMessageSame as SendMessageMessage, but with an expiration to be passed to the router As of 0.8.4, retrofitted to use DateAndFlags. SendMessageMessageDefines the message a client sends to a router to ask it to deliver a new message SessionConfigDefines the information a client must provide to create a session SessionIdDefines the token passed between the router and client to associate messages with a particular session. SessionStatusMessageDefines the message a router sends to a client indicating the status of the session. SetDateMessageTell the other side what time it is.
Exception Summary Exception Description I2CPMessageExceptionRepresent an error serializing or deserializing a message