uuid

I'm looking for a solution for a Java based webapplication to uniquely identify the client. The server is in the same network as the clients and I thought that using the MAC address would be a good solution. The problem is I can't work with cookies because they can be deleted client-side and I can't use the IP because they could just issue a new DHCP lease renewal. So I would like to fallback to the MAC address of the clients. I'm aware that there is no java built in feature to get the MAC address. Is there a library that can handle the output of every OS? (primary Windows and Mac) since my

I'm trying to add UUIDs to a couple of tables, but I'm not sure what the best way to store/retrieve these would be. I understand it's far more efficient to use BINARY(16) instead of VARCHAR(36). After doing a bit of research, I also found that you can convert a UUID string to binary with: UNHEX(REPLACE(UUID(),'-','')) Pardon my ignorance, but is there an easy way to this with PHP and then turn it back to a string, when needed, for readability? Also, would it make much difference if I used this as a primary key instead of auto_increment? EDIT: Found part of the answer: $bin = pack("h*", str

I would like to use a GIN index on uuid[] (to have efficient membership tests for arrays of uuids). However when I try it PostgreSQL gives me an error: mydb=> CREATE TABLE foo (val uuid[]); CREATE TABLE mydb=> CREATE INDEX foo_idx ON foo USING GIN(val); ERROR: data type uuid[] has no default operator class for access method "gin" HINT: You must specify an operator class for the index or define a default operator class for the data type. How can I add the necessary operator class so that it works? Note that this is a similar question for the type citext but the provided answer doesn't work.

I'm generating UUIDs using PHP, per the function found here Now I want to store that in a MySQL database. What is the best/most efficient MySQL field format for storing UUID v4? I currently have varchar(256), but I'm pretty sure that's much larger than necessary. I've found lots of almost-answers, but they're generally ambiguous about what form of UUID they're referring to, so I'm asking for the specific format. Store it as VARCHAR(36) if you're looking to have an exact fit, or VARCHAR(255) which is going to work out with the same storage cost anyway. There's no reason to fuss over bytes here.

I am developing an application which uses Bluetooth to connect to a device and send/receive data. I am doing all of my testing with a Nexus One phone. I have never been able to establish a SPP (serial port) connection from my phone to any device. However, I have been able to connect from a device (my laptop) to my phone using a Mac equivalent of PuTTY (The only exception to this is the "Bluetooth File Transfer" app from the Marketplace seems to work, but I don't think that uses RFCOM/SPP...). I keep seeing this message in my LogCat logs: ERROR/BluetoothService.cpp(78): stopDiscoveryNative: D

I have multiple projects in a single Visual Studio (2008) solution. I just discovered that each of these projects uses a same GUID, so in the solution file it looks like this: Project("{FAE04EC0-F103-D311-BF4B-00C04FCBFE97}") = "Pro1", "Pro1\Pro1.csproj", "{...}" Project("{FAE04EC0-F103-D311-BF4B-00C04FCBFE97}") = "Pro2", "Pro2\Pro2.csproj", "{...}" Do I have to change these GUIDs so they're unique and what are they used for? Project persistence block in a solution file has the following format: Project("{project type GUID}") = "<Project name>", "<project file location>", "{<Unique project