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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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19.3.1 Binding to <strong>TCP</strong><br />

client-to-server protocol, in practice, the system consists of a network of servers<br />

that inter-communicate. Therefore, for example, is able<br />

to exchange messages, presence, other information with<br />

. This pattern is familiar <strong>and</strong> from messaging protocols<br />

(such as SMTP) that make use of network addressing st<strong>and</strong>ards.<br />

Communications between any two servers are optional. If enabled, such<br />

communications occur over XML streams that are bound to <strong>TCP</strong> connections.<br />

The recommended port for connections between servers is 5269, as registered<br />

with the IANA.<br />

Although there is no necessary coupling of an XML stream to a <strong>TCP</strong> connection<br />

(for example, two entities can connect to each other through another mechanism<br />

such as polling over HTTP), this specification addressed in RFC 3920 defines a<br />

binding of XMPP to <strong>TCP</strong> only. In the context of client-to-server communications,<br />

a server must allow a client to share a single <strong>TCP</strong> connection for XML stanzas<br />

sent from client to server <strong>and</strong> from server to client. In the context of<br />

server-to-server communications, a server must use one <strong>TCP</strong> connection for<br />

XML stanzas sent from the server to the peer <strong>and</strong> another <strong>TCP</strong> connection<br />

(initiated by the peer) for stanzas from the peer to the server, for a total of two<br />

<strong>TCP</strong> connections.<br />

19.3.2 Address resolution<br />

A client determines the <strong>IP</strong> address of an appropriate system running on a server<br />

by resolving the destination domain name, which is part of the identifier within the<br />

presence tuple, to either an intermediate relay system or a final target system.<br />

This is discussed further in RFC 3861.<br />

19.4 RFCs relevant to this chapter<br />

The following RFCs provide detailed information about the presence services<br />

<strong>and</strong> concepts presented throughout this chapter:<br />

► RFC 2426 – vCard MIME Directory Profile (September 1998)<br />

► RFC2778 – A Model for Presence <strong>and</strong> Instant Messaging (February 2000)<br />

► RFC 2779 – Instant Messaging / Presence Protocol Requirements<br />

(February 2000)<br />

► RFC 2849 – The LDAP Data Interchange Format (LDIF) - <strong>Technical</strong><br />

Specification (June 2000)<br />

718 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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