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SunOS 5.5 Protocols tcp(7P)

NAME tcp, TCP − Internet Transmission Control Protocol

SYNOPSIS #include <sys/socket.h>

#include <netinet/in.h>

s = socket(AF_INET, SOCK_STREAM, 0);

t = t_open("/dev/tcp", O_RDWR);

DESCRIPTION TCP is the virtual circuit protocol of the Internet protocol family. It provides reliable,

ﬂow-controlled, in order, two-way transmission of data. It is a byte-stream protocol lay-

ered above the Internet Protocol (IP), the Internet protocol family’s internetwork

datagram delivery protocol.

Programs can access TCP using the socket interface as a SOCK_STREAM socket type, or

using the Transport Level Interface (TLI) where it supports the connection-oriented

(T_COTS_ORD) service type.

TCP usesIP’s host-level addressing and adds its own per-host collection of “port

addresses.” The endpoints of a TCP connection are identiﬁed by the combination of an IP

address and a TCP port number. Although other protocols, such as the User Datagram

Protocol (UDP), may use the same host and port address format, the port space of these

protocols is distinct. See inet(7P) for details on the common aspects of addressing in the

Internet protocol family.

Sockets utilizingTCP are either “active” or “passive”. Active sockets initiate connections

to passive sockets. Both types of sockets must have their local IP address and TCP port

number bound with the bind(3N) system call after the socket is created. By default, TCP

sockets are active. A passive socket is created by calling the listen(3N) system call after

binding the socket with bind(). This establishes a queueingparameter for the passive

socket. After this, connections to the passive socket can be received with the accept(3N)

system call. Active sockets use the connect(3N) call after binding to initiate connections.

By using the special value INADDR_ANY, the local IP address can be left unspeciﬁed in

the bind() call by either active or passive TCP sockets. This feature is usually used if the

local address is either unknown or irrelevant. If left unspeciﬁed, the localIP address will

be bound at connection time to the address of the network interface used to service the

connection.

Once a connection has been established, data can be exchangedusing the read(2) and

write(2) system calls.

TCP supports one socket option which is set with setsockopt() and tested with

getsockopt(3N). Under most circumstances, TCP sends data when it is presented. When

outstanding data has not yet been acknowledged, it gathers small amounts of output to

be sent in a single packet once an acknowledgementis received. For a small number of

clients, such as window systems that send a stream of mouse events which receive no

replies, this packetization may cause signiﬁcant delays.

modiﬁed 3 Jul 1990 7P-341

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Adaptec AHA-1520A Manual de Serviço Página 345