Class TCPOpenCommand

File: src/transport/contract/TCPCommand.msg

Control info to be used for active or passive TCP open.

localAddr, remoteAddr, localPort, remotePort should be self-explanatory. localAddr is optional because TCP can learn it from IP when a packet is received from the peer; localPort is optional because TCP supports ephemeral ports.

The sendQueueClass, receiveQueueClass and tcpAlgorithmClass fields allow per-connection TCP configuration. These fields may contain names of classes subclassed from TCPSendQueue, TCPReceiveQueue and TCPAlgorithm, respectively. If not set, module parameters with similar names are used.

The fork parameter is used with passive open, and controls what happens when an incoming connection is received. With fork=true, it emulates the Unix accept(2) syscall semantics: a new connection structure is created for the connection (with a new connId, see in TCPCommand), and the connection structure with the old connId remains listening. With fork=false, all the above does not happen: the first connection is accepted (with the original connId), and further incoming connections will be refused by TCP by sending an RST segment.

See also: TcpCommandCode, TCP

Usage diagram:

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Inheritance diagram:

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Extends:

TCPCommand (class)

Control info for TCP connections. This class is to be set as control info (see cMessage::setControlInfo()) on all messages exchanged between TCP and application, in both directions. Some commands and indications (TCP_C_OPEN_xxx, TCP_I_STATUS) use subclasses.

Fields:

Name	Type	Description
fork	bool	used only for passive open
connId	int	identifies the socket within the application
receiveQueueClass	string	may be left empty
userId	int	id than can be freely used by the app
tcpAlgorithmClass	string	may be left empty
localPort	int	required for passive open
remotePort	int	required for active open
localAddr	IPvXAddress	may be left empty
sendQueueClass	string	may be left empty
remoteAddr	IPvXAddress	required for active open

Source code:

//
// Control info to be used for active or passive TCP open.
//
// localAddr, remoteAddr, localPort, remotePort should be self-explanatory.
// localAddr is optional because TCP can learn it from IP when a packet
// is received from the peer; localPort is optional because TCP supports
// ephemeral ports.
//
// The sendQueueClass, receiveQueueClass and tcpAlgorithmClass fields
// allow per-connection TCP configuration. These fields may contain
// names of classes subclassed from TCPSendQueue, TCPReceiveQueue
// and TCPAlgorithm, respectively. If not set, module parameters with
// similar names are used.
//
// The fork parameter is used with passive open, and controls what happens
// when an incoming connection is received. With fork=true, it emulates
// the Unix accept(2) syscall semantics: a new connection structure
// is created for the connection (with a new connId, see in TCPCommand),
// and the connection structure with the old connId remains listening.
// With fork=false, all the above does not happen: the first connection
// is accepted (with the original connId), and further incoming connections
// will be refused by TCP by sending an RST segment.
//
// @see TcpCommandCode, TCP
//
class TCPOpenCommand extends TCPCommand
{
    IPvXAddress localAddr; // may be left empty
    IPvXAddress remoteAddr;// required for active open
    int localPort = -1;       // required for passive open
    int remotePort = -1;      // required for active open
    bool fork = false;        // used only for passive open
    string sendQueueClass;    // may be left empty
    string receiveQueueClass; // may be left empty
    string tcpAlgorithmClass; // may be left empty
}