jabber-network-server is the hostname or IP address of your
server. If it is set to nil, jabber.el will use the name in
jabber-server.
jabber-port is the TCP port of the server to connect to. If
nil, the default port is selected based on the chosen
connection method.
jabber-connection-type specifies what kind of connection to
use. network means normal unencrypted network connection
(usually on port 5222), and ssl means encrypted connection
through GnuTLS or OpenSSL (port 5223). You can change the settings of
the encryption program through M-x customize-group RET tls or
M-x customize-group RET ssl, respectively.
By default, GnuTLS will be used if the tls library is available,
and if that fails, OpenSSL will be used if the ssl library is
available. You can force the use of either program by setting
jabber-connection-ssl-program to gnutls or openssl,
respectively.