ITcp

module interface

Interface for TCP protocol implementations. All TCP implementations should implement this (i.e. declared as: TCP like ITcp) The existing implementations are these: Tcp, TcpLwip, (and TcpNsc in the inet-gpl project).

Communication with applications

For communication between applications and TCP, the TcpCommandCode and TcpStatusInd enums are used as message kinds, and TcpCommand and its subclasses are used as control info.

To open a connection from a client app, send a cMessage to TCP with TCP_C_OPEN_ACTIVE as message kind and a TcpOpenCommand object filled in and attached to it as control info. (The peer TCP will have to be LISTENing; the server app can achieve this with a similar cMessage but TCP_C_OPEN_PASSIVE message kind.) With passive open, there's a possibility to cause the connection "fork" on an incoming connection, leaving the original connection LISTENing on the port (see the fork field in TcpOpenCommand).

The app can send data by assigning the TCP_C_SEND message kind to the data packet, and sending it to TCP. The app will receive data as messages with the TCP_I_DATA message kind.

To close, the client sends a cMessage to TCP with the TCP_C_CLOSE message kind and TcpCommand control info.

TCP sends notifications to the application whenever there's a significant change in the state of the connection: established, remote TCP closed, closed, timed out, connection refused, connection reset, etc. These notifications are also cMessages with message kind TCP_I_xxx (TCP_I_ESTABLISHED, etc.) and TcpCommand as control info.

One TCP module can serve several application modules, and several connections per application. When talking to applications, a connection is identified by the connId that is assigned by the application in the OPEN call.

Sockets

The TcpSocket C++ class is provided to simplify managing TCP connections from applications. TcpSocket handles the job of assembling and sending command messages (OPEN, CLOSE, etc) to TCP, and it also simplifies the task of dealing with packets and notification messages coming from TCP.

Communication with the IP layer

A TCP header is represented by the class TcpHeader.

The TCP model relies on sending and receiving L3AddressReq/L3AddressInd tags attached to TCP segment packets.

Inheritance diagram

The following diagram shows inheritance relationships for this type. Unresolved types are missing from the diagram.

Implemented by

Name	Type	Description
Tcp	simple module	TCP protocol implementation. See the ITcp for the Tcp layer general informations.
TcpLwip	simple module	TCP model based on the LWIP 1.3.2 project. The original LWIP is available on this page.
TcpSpoof	simple module	Sends fabricated TCP packets. This is a base implementation, you'll probably have to customize it in C++ according to what you want to send and when you want to send it.

Used in compound modules

Name	Type	Description
LdpMplsRouter	compound module	An LDP-capable router.
TransportLayerNodeBase	compound module	(no description)

Properties

Name	Value	Description
display	i=block/wheelbarrow

Source code

//
// Interface for TCP protocol implementations. All TCP implementations should
// implement this (i.e. declared as: TCP like ITcp)
// The existing implementations are these: ~Tcp, ~TcpLwip, (and ~TcpNsc in the inet-gpl project).
//
// <b>Communication with applications</b>
//
// For communication between applications and TCP, the ~TcpCommandCode
// and ~TcpStatusInd enums are used as message kinds, and ~TcpCommand
// and its subclasses are used as control info.
//
// To open a connection from a client app, send a cMessage to TCP with
// TCP_C_OPEN_ACTIVE as message kind and a ~TcpOpenCommand object filled in
// and attached to it as control info. (The peer TCP will have to be LISTENing;
// the server app can achieve this with a similar cMessage but TCP_C_OPEN_PASSIVE
// message kind.) With passive open, there's a possibility to cause the connection
// "fork" on an incoming connection, leaving the original connection LISTENing
// on the port (see the fork field in ~TcpOpenCommand).
//
// The app can send data by assigning the TCP_C_SEND message kind to the data packet,
// and sending it to TCP. The app will receive data as messages
// with the TCP_I_DATA message kind.
//
// To close, the client sends a cMessage to TCP with the TCP_C_CLOSE message kind
// and ~TcpCommand control info.
//
// TCP sends notifications to the application whenever there's a significant
// change in the state of the connection: established, remote TCP closed,
// closed, timed out, connection refused, connection reset, etc. These
// notifications are also cMessages with message kind TCP_I_xxx
// (TCP_I_ESTABLISHED, etc.) and ~TcpCommand as control info.
//
// One TCP module can serve several application modules, and several
// connections per application. When talking to applications, a
// connection is identified by the connId that is assigned by the application in
// the OPEN call.
//
// <b>Sockets</b>
//
// The TcpSocket C++ class is provided to simplify managing TCP connections
// from applications. TcpSocket handles the job of assembling and sending
// command messages (OPEN, CLOSE, etc) to TCP, and it also simplifies
// the task of dealing with packets and notification messages coming from TCP.
//
// <b>Communication with the IP layer</b>
//
// A TCP header is represented by the class ~TcpHeader.
//
// The TCP model relies on sending and receiving ~L3AddressReq/~L3AddressInd tags
// attached to TCP segment packets.
//
moduleinterface ITcp
{
    @display("i=block/wheelbarrow");
    gates:
        input appIn @labels(TcpCommand/down);
        input ipIn @labels(TcpHeader,Ipv4ControlInfo/up,Ipv6ControlInfo/up);
        output appOut @labels(TcpCommand/up);
        output ipOut @labels(TcpHeader,Ipv4ControlInfo/down,Ipv6ControlInfo/down);
}

File: src/inet/transportlayer/contract/ITcp.ned