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<concept id="GUID-A9640739-462C-5D95-8DCC-D273CD8439AE" xml:lang="en"><title>TCP/IP</title><shortdesc>This section describes the TCP/IP concepts as implemented by the

Symbian platform. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The TCP/IP is a plug-in architecture. Clients access its services through

the generic Sockets Server Client API, and specify protocol-specific behaviour

through TCP/IP specific utility types and constants. </p>

<p>The TCP/IP API has the following three key concepts: </p>

<ul>

<li id="GUID-7D1C1EC3-87D6-5C30-9671-63CDF8CDC05A"><p>TCP/IP Socket </p> </li>

<li id="GUID-1412D36F-1834-56E7-A904-8C5577BFD841"><p>Domain Name Resolver </p> </li>

<li id="GUID-A2A04887-0E9E-5A94-BD78-CAD2CB720343"><p>Internet Addresses </p> </li>

</ul>

<section id="GUID-6EDFE283-E780-4A9B-93B4-5E1FEA0EE906"><title>TCP/IP Socket</title> <p>The TCP/IP protocol module (tcpip.prt)

provides TCP/IP communication services to client applications. This module

provides the following four fundamental transport and network layer protocols: </p> <ul>

<li id="GUID-4EE43C12-9065-5B5A-8DA1-C1D299408E41"><p>Internet Protocol (IP) <xref href="http://www.ietf.org/rfc/rfc791.txt" scope="external">RFC791</xref>  </p> </li>

<li id="GUID-8219260F-D83C-575B-B92B-A9FF30E06100"><p>Internet Control Message

Protocol (ICMP) <xref href="http://www.ietf.org/rfc/rfc792.txt" scope="external">RFC792</xref> and <xref href="http://www.ietf.org/rfc/rfc950.txt" scope="external">RFC950</xref>  </p> </li>

<li id="GUID-18E9FDB7-EB17-5DEB-B075-6840F72B9F11"><p>Transmission Control

Protocol (TCP) <xref href="http://www.ietf.org/rfc/rfc793.txt" scope="external">RFC793</xref>  </p> </li>

<li id="GUID-509BB14D-7EF9-5768-A992-4A08B23204A5"><p>User Datagram Protocol

(UDP) <xref href="http://www.ietf.org/rfc/rfc768.txt" scope="external">RFC768</xref>  </p> </li>

</ul> <p>Clients do not access the protocol module directly. Clients use the

protocol module through the Sockets Server Client API. The module also provides

a DNS service that can be accessed through the Sockets Server Client API standard

host name resolution interface, <xref href="GUID-5442E589-1BFB-39A0-98B3-3744E51F8386.dita"><apiname>RHostResolver()</apiname></xref>. Socket

services are provided through the generic interface <xref href="GUID-66497E39-6A48-3B2C-BE17-5826210505AB.dita"><apiname>RSocket()</apiname></xref>.

It is possible for TCP/IP services to be used over many types of network interface.

To enable access to TCP/IP networks through a dial-up serial connection, Point-to-Point

protocol (PPP) is provided. </p> </section>

<section id="GUID-DCC92F00-9743-48D5-B93D-6CD61872F428"><title>Domain Name Resolver</title> <p>Domain name resolver is a

program that extracts the information from name servers in response to client

requests. The domain name resolution service uses the normal sockets API,

for example, UDP and TCP to communicate with the name servers. Resolvers must

access at least one name server and uses its information to answer a query

directly. A resolver is a system procedure that is accessible to the user

programs, for example, mail programs, TELNET and FTP. This indicates that

the protocol is not required between the resolver and the user programs. </p> <p>A

very important goal of the resolver is to eliminate the network delay and

the load on the name server. </p> </section>

<section id="GUID-62DA50B4-EA55-4975-9F35-D9C5F572E002"><title>Internet Addresses</title> <p>The TCP/IP program uses a socket

address encapsulated in a <codeph>TInetAddr</codeph> object. The <codeph>TInetAddr</codeph> object

stores the IP address and port of a socket. This is the expected form for

passing address information when using <codeph>RSocket()</codeph> and <codeph>RHostResolver()</codeph> for

TCP/IP. </p> <p>The TCP/IP program also handles IP addresses represented in

the following formats: </p> <ul>

<li id="GUID-0310B249-26DE-53E6-AA50-BEE114EA6E53"><p>As a dotted-decimal

string, For example, 194.129.2.54 stored in a descriptor. </p> </li>

<li id="GUID-D5BCC6F8-954D-564C-B9D6-032FED950F8F"><p>As an unsigned 32-bit

integer - the usual binary representation of an IP address. This can be used

to initialise a <codeph>TInetAddr</codeph> through the relevant constructor. </p> </li>

<li id="GUID-C683FEEC-C3F5-5542-8AAA-2E1A76F3E1C5"><p>The 4 integers forms

a dotted-decimal address and the macro INET_ADDR is used to convert this into

integer format in the appropriate byte-order. </p> </li>

</ul> <p> <b>Note:</b> All addresses are handled in the native byte order.

It means the user do not need to use byte-order conversion functions, for

example, BSD’s <xref href="GUID-1E24E920-D34A-38D4-98B1-6AE44B98113C.dita"><apiname>htonl()</apiname></xref> or <xref href="GUID-013170BC-E395-3887-8EE1-BBDBE5AD8C31.dita"><apiname>htons()</apiname></xref>. </p> </section>

<section id="GUID-3D557650-275B-4359-8A61-03A345EEF947"><title>Routes and Interfaces</title> <p>The TCP/IP protocol must

establish the following information to communicate with a remote host through

a socket: </p> <ul>

<li id="GUID-F9ABF503-6687-5B87-A082-C0844A36C0E6"><p>the IP address and port

of the socket </p> </li>

<li id="GUID-D3423B61-CBE1-58A4-83EF-9AD18BB018EE"><p>a route to the remote

host </p> </li>

<li id="GUID-85BA7CE9-93E0-58A7-A9D1-5E15FBF523FF"><p>a network interface

by which to access that route </p> </li>

</ul> <p>The actions to do this are performed when: </p> <ul>

<li id="GUID-FA6AD28F-3EC9-5429-B5DE-CAEAF1633CDA"><p>A TCP socket is connected

with <xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita#GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0/GUID-AC5A49E9-337D-334A-9CD0-DB8226372306"><apiname>RSocket::Connect()</apiname></xref>  </p> </li>

<li id="GUID-02FA2CD0-AD09-5E9F-AF10-6018AA9D6001"><p>a UDP socket is written

to with <xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita#GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0/GUID-ADE2383D-3075-30B4-8F63-6D837EB75AEF"><apiname>RSocket::Send()</apiname></xref>, <xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita#GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0/GUID-29825F33-D844-358A-8CCA-791AE167CDCE"><apiname>RSocket::Write()</apiname></xref> or <xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita#GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0/GUID-F948E0A6-DC1A-3FCD-A391-0FEE0F673D36"><apiname>RSocket::SendTo()</apiname></xref>  </p> </li>

<li id="GUID-53FC4772-8A69-5514-A3F1-48E0FF1CC305"><p>A UDP socket is connected

with <xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita#GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0/GUID-AC5A49E9-337D-334A-9CD0-DB8226372306"><apiname>RSocket::Connect()</apiname></xref>  </p> </li>

</ul> </section>

</conbody><related-links>

<link href="GUID-B8DEA3EE-7BA7-5A29-9A27-B87EE0EB254F.dita"><linktext>Accessing

TCP/IP Sockets</linktext></link>

<link href="GUID-182A7A60-80BD-5E54-917A-8F4C26BB94CB.dita"><linktext> Connecting

and                 Disconnecting a remote host</linktext></link>

<link href="GUID-3AAE78A4-75C5-5607-8775-43DFB43DCFE8.dita"><linktext> Getting

and Setting IP                 Addresses</linktext></link>

<link href="GUID-95C166C3-2A25-55FB-88BD-62B7EFED2F8E.dita"><linktext> Using Domain

Name                 Resolution</linktext></link>

</related-links></concept>