OverviewIn the previous article titled Why TCP needs 3 handshakes simple answers were provided to the following three questions:Can application data be carried during the first handshake?Can application data be carried during the second handshake?Can application data be carried during the third handshake?Briefly, traditional TCP requires a three-way handshake to establish a connection, and during these three handshakes, only simple SYN and ACK packets are sent.From the perspective of utilizing network bandwidth resources, the TCP header at the transport layer plus the IP header at the net...

Prerequisite KnowledgeFirst, let's look at the control bits and state machine of TCP, which form the basis for understanding the three-way handshake of TCP.TCP Packet Control BitsThe control bits in the TCP packet header are used to control the status of the TCP connection and can indicate various control information such as connection establishment, termination, reset, etc.There are six common control bits:SYN (Synchronize Sequence Numbers): Requests to establish a connection (part of the three-way handshake). It is set in the initial packet during connection establishment, indicating that th...

Keep table column as NOT NULL instead of NULL except in some special cases. This statement is cited by many articles of MySQL optimization, but they don't say why we should do this. Here we discuss about this.First why are there many people using NULL when defining table? The reasons may be:NULL the the default when defining table, the rookies or people who don't want to have much troubles will keep this default settingMany people think NOT NULL will require more spaceMany people don't want to verify the data before inserting or updating, it's more convenient when writing SQL queries.There are...

I realized that, paradoxically enough, good programmers need to be both lazy and dumb.Lazy, because only lazy programmers will want to write the kind of tools that might replace them in the end. Lazy, because only a lazy programmer will avoid writing monotonous, repetitive code – thus avoiding redundancy, the enemy of software maintenance and flexible refactoring. Mostly, the tools and processes that come out of this endeavor fired by laziness will speed up the production.This makes a lazy programmer a good programmer. Of course, this is only half the truth; for a lazy programmer to be ...

Sales of desktop PCs and laptops are falling. It’s impossible to read any technical media without hearing about the “death of the PC.” And both Apple and Microsoft are soon to release operating systems that seek to merge the features of the computer operating system with those available on tablet devices.All this evidence mounts up to suggest that the Steve Jobs-coined “post PC era” is upon us. Well, I’m going to stick my neck out on this: I don’t buy it.Don’t get me wrong – I possess and adore an iPhone 4s, and if I need to quickly lo...

As an active member of "The Internet" and vocal Objective-C coder, I get a lot of questions surrounding the language. They're often framed around thinking about learning the language or trying to write an app, but they also usually involve a phrase like "Objective-C looks really hard" or "what are all those minus signs about?" Both of these are pretty good questions, and I'd like to address why someone might be more hesitant to jump into iOS or OS X development compared to, say, Ruby or Java.SyntaxLet's talk about what a programming language is. A programming language is the human-readable cod...

The physicist Niels Bohr once defined an expert as “a person who has made all the mistakes that can be made in a very narrow field.” Bohr’s quip summarizes one of the essential lessons of learning, which is that people learn how to get it right by getting it wrong again and again. Education isn’t magic. Education is the wisdom wrung from failure.A new study, forthcoming in Psychological Science, and led by Jason Moser at Michigan State University, expands on this important concept. The question at the heart of the paper is simple: Why are some people so much more effe...

I prefer to come into work a little earlier before our 9 a.m. start time in order to leave before 5 p.m. My boss has no problem with my hours, though an older female colleague apparently does. She regularly tells me that this “special” work schedule is damaging my career trajectory and conveys to others that I am a diva. To that I reply, according to whom?There are many workplace assumptions that employees accept without question. Why does the traditional work day start at 9 a.m? Who decided 14 days is the proper amount of annual vacation time? Why do employees need to give a two-w...