Documentation Contents

# Networking Properties

## System Properties

See Network System Properties for a list of system properties used to alter the mechanisms and behavior of the various classes of the `java.net` package.

## JDK Implementation-Specific Properties

These properties may not be supported in future releases.

- `sun.net.inetaddr.ttl`
  This is a Oracle JDK private system property that corresponds to `networkaddress.cache.ttl`. It takes the same value and has the same meaning, but can be set as a command-line option. However, the preferred way is to use the security property `networkaddress.cache.ttl`.

- `sun.net.inetaddr.negative.ttl`
  This is a Oracle JDK private system property that corresponds to `networkaddress.cache.negative.ttl`. It takes the same value and has the same meaning, but can be set as a command-line option. However, the preferred way is to use the security property `networkaddress.cache.negative.ttl`.

- `sun.net.client.defaultConnectTimeout` (default: `-1`)
  `sun.net.client.defaultReadTimeout` (default: `-1`)
  These properties specify the default connect and read timeout, respectively, for the protocol handler used by `java.net.URLConnection`.

  `sun.net.client.defaultConnectTimeout` specifies the timeout (in milliseconds) to establish the connection to the host. For example for HTTP connections, it is the timeout when establishing the connection to the HTTP server. For FTP connections, it is the timeout when establishing the connection to FTP servers.

  `sun.net.client.defaultReadTimeout` specifies the timeout (in milliseconds) when reading from input stream when a connection is established to a resource.

- `sun.net.http.retryPost` (default: `true`)
  It determines if an unsuccessful HTTP POST request will be automatically resent to the server. Unsuccessful in this case means the server did not send a valid HTTP response or an `IOException` occurred.

## JNDI DNS Service Provider Settings

These properties may not be supported in future releases.

- `sun.net.spi.nameservice.provider.<n>=<default|dns,sun|...>`
  Specifies the name service provider that you can use. By default, the JDK will use the system configured name lookup mechanism, such as `file`, `nis`, etc. You can specify your own by setting this option. `<n>` takes the value of a positive number. It indicates the precedence order. A smaller number takes higher precedence over a bigger number. Aside from the default provider, the JDK includes a DNS provider named `dns,sun`.

  Providers are chained, which means that if a lookup on a provider fails, the next provider in the list is consulted to resolve the name.

- `sun.net.spi.nameservice.nameservers=<server1_ipaddr,server2_ipaddr ...>`
  You can specify a comma-separated list of IP addresses that point to the DNS servers you want to use. If the `sun.net.spi.nameservice.nameservers property` is not defined, then the provider will use any name servers already configured in the platform DNS configuration.

- `sun.net.spi.nameservice.domain=<domainname>`
  This property specifies the default DNS domain name, for instance, `eng.example.com`. If the `sun.net.spi.nameservice.domain` property is not defined then the provider will use any domain or domain search list configured in the platform DNS configuration.

Copyright © 1993, 2026, Oracle and/or its affiliates. All rights reserved.
Contact Us