Maximum tcp port number constant in java

Question

Is there a public constant for the maximum TCP port number (65535) defined in java or a common library such as Apache Commons, that I could refer to from my code (instead of using the integer hardcoded)?

Answer 1

I'm afraid there is none you can use.

Looking at the source code of Java 8 I see the following code used by the Socket class to verify a valid port in several functions:

private static int checkPort(int port) {
    if (port < 0 || port > 0xFFFF)
        throw new IllegalArgumentException("port out of range:" + port);
    return port;
}

This can be found in java.net.InetSocketAddress.checkPort(int)

As you can see Java itself doesn't use a named constant either.

A search of the code turns up the following hit in java.net.HostPortrange:

static final int PORT_MIN = 0;
static final int PORT_MAX = (1 << 16) -1;

But as you can see this isn't a public reference. Another private reference turns up in java.net.SocketPermission.

So after the inspection above, I conclude there is none available in the Java API.