tcp(6P)                        DG/UX R4.11MU05                       tcp(6P)


NAME
       TCP - Network Protocol Internet Transmission Control Protocol

SYNOPSIS
       #include <sys/socket.h>
       #include <netinet/tcp.h>

       This is an example of how you would create an endpoint for the TCP
       connection:

           s = socket(AFINET, SOCKSTREAM, 0);

DESCRIPTION
       Transmission Control Protocol (TCP) provides reliable, flow-
       controlled, two-way transmission of data.  It is a byte-stream
       protocol used to support the SOCK_STREAM abstraction.  TCP provides a
       per-host collection of port addresses on top of the standard Internet
       address format.  Thus, each address is composed of an Internet
       address specifying the host and network, with a specific TCP port on
       the host identifying the peer entity.

       Sockets utilizing the TCP are either "active" or "passive".  Active
       sockets initiate connections to passive sockets.  By default TCP
       sockets are created active; only active sockets may use the
       connect(2) call to initiate connections.  To create a passive socket,
       the listen(2) system call must be used after binding the socket with
       the bind(2) system call.  Only passive sockets may use the accept(2)
       call to accept incoming connections.

       Passive sockets may "underspecify" their location to match incoming
       connection requests from multiple networks.  This technique, termed
       "wildcard addressing", allows a single server to provide service to
       clients on multiple networks.  To create a socket that listens on all
       networks, the Internet address INADDR_ANY must be bound to the
       socket.  The TCP port may still be specified at this time; if the
       port is not specified, the system will assign one.  Once a connection
       has been established, the socket's address is fixed by the peer
       entity's location.  The address assigned to the socket is the address
       associated with the network interface through which packets are being
       transmitted and received.

OPTIONS
       IPPROTO_TCP level options recognized by TCP:

       TCP_NODELAY         When the option value is non-zero, the system
                           does not delay sending data to coalesce small
                           packets.  When the option value is zero, the
                           system may defer sending data to coalesce small
                           packets to conserve network bandwidth.

       TCP_MAXSEG          When set prior to a connect(2) call, TCP will use
                           the option value to negotiate the maximum size of
                           TCP packets sent and received during the life of
                           the connection.  Values for the TCP Maximum
                           Segment Size are between 1 and 65,535.  This
                           option is only valid prior to establishing a
                           connection.  The result of segment size
                           negotiation is less than or equal to the option
                           value.

       TCP_URGENT_INLINE   This option has no effect in the DG/UX system.
                           Use the SO_OOBINLINE socket level option.

       TCP_PEER_ADDRESS    Restricts the passive TCP endpoint to only accept
                           connections initiated by the address supplied in
                           the option value.  The option value must contain
                           a pointer to a sockaddr_in structure.

       TCP_ACCEPT_QUEUE_LENGTH
                           Sets the number of outstanding connections
                           allowed at the TCP passive endpoint.

SEE ALSO
       getsockopt(2), setsockopt(2), intro(6), inet(6F), ip(6P).
       Programming with TCP/IP on the DG/UX System.


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