What's the connection timeout of a socket created with a connecting constructor?

Question

What's the connection timeout of a socket created with a connecting constructor?

In Java SE 6, the following constructors for Socket will connect the socket right away instead of you having to call connect on it after construction:

• Socket(InetAddress address, int port)
• Socket(InetAddress host, int port, boolean stream)
• Socket(InetAddress address, int port, InetAddress localAddr, int localPort)
• Socket(String host, int port)
• Socket(String host, int port, boolean stream)
• Socket(String host, int port, InetAddress localAddr, int localPort)

While it's nice and convenient and all that the Java SE folks created 500 ways of constructing a socket so you can just browse the list of 500 to find the one that sort of does what you want (instead of calling new Socket() followed by Socket#connect()), none of the docs of these constructors says what the connection timeout is or whether/how they call connect(SocketAddress endpoint, int timeout).

Perhaps the stuff in the constructor docs talking about createSocketImpl imply something about the timeout, or some docs somewhere else say it?

Anyone know what the actual connection timeout for any of these constructors is?

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Background: Okay, assuming the spec is really ambiguous (I thought Java is portable?), I'm trying to figure out why a customer's code freezes at seemingly random times. I have some code that calls some open source library which calls one of these constructors. I want to know whether calling one of these constructors would have made the timeout infinite or very long. I don't know what version of the JDK the customer is using so it would be nice if the spec says the timeout somewhere. I guess I can probably get the JDK version from my customer, but it will probably be the closed source JDK. In that case, could I reverse-engineer the code in their version of the SE library to find out? Is it hard? Will I go to jail?

Answer 1

Java spec is bogus. It doesn't say what timeout is on any of those constructor so implementation could set timeout to 0.000000000001 nanoseconds and still be correct. Furthurmore: non finite timeout not even respected by vm implementations (as seen here) so look like spec doesnt even matter cause noone followed it.

Conclusion: You have to read closed source binary of customer JVM (probably illegal but you have to do what you have to do), also OS socket doc.

Answer 2

Even though Java docs says the timeout is infinite, it actually means that JVM will not impose any timeout on the connect operation, however OS is free to impose timeout settings on any socket operations.

Thus the actual timeout will be dependent on your OS's TCP/IP layer settings.

A good programming practice is to set timeouts for all socket operations, preferably configurable via configuration file. The advantage of having it configurable is that depending on the network load of the deployment environment, the timeout can be tweaked without re-building/re-testing/re-releasing the whole software.