Thursday, November 24, 2011

CSS Tips For Beginner Web Designers

First and foremost, Happy Thanksgiving! I've decided to write up a short blog of web design tips and tricks.

Recently I was asked to do some work on the website for my undergraduate research project. I have very limited experience designing things from scratch with HTML/CSS, so I decided to turn the website itself in to a learning experience. I decided I wanted to build the website from the ground up, using no templates and no fancy graphical editors like Dreamweaver. I wanted to understand exactly what made my website look the way it looked.

I also decided that I did not want to use any images. CSS3 provides some really cool attributes that let you do some neat stuff that normally would require an image.

I've done some very basic web development and ASP stuff in the past, but I've never really bothered using much CSS and considering how widely it is used today, I thought it might be important to learn.

So here are my tips.
  • Use as a resource. I have always avoided using this site when looking up things because (ironically) I did not like the site layout and the ads were a bit much for my likings. On closer inspection, I found that this website really had a lot to offer me. I highly recommend the CSS section.
  • Use jsFiddle as a crutch while learning HTML and CSS. jsFiddle is a very simple, yet incredible editor for making quick prototypes of websites. You get 3 editor panels, one for HTML, CSS, and Javascript. The fourth panel shows you a preview of what your website actually looks like. I can not emphasize enough how great this tool is and how much it has helped me understand how CSS and HTML work together in just a few days of "fiddling".
  • Use Google to search for websites to draw from for inspiration. I do not have an eye for visual design, so this was a 'must' for me. I wanted my website to look modern, not like a geocities website from the 90's. I searched for Web 2.0 example sites and templates and found some design guidelines. I didn't follow the design guidelines exactly, since I needed to maintain a certain degree of professionalism for a school website, but it did give me some ideas to help me along in my design process.
  • Search for CSS generators. Some of the newer CSS3 features may be harder to figure out how to use, and there are tons of generators out there that will help you get the look that you want. Also, most of these generators will generate browser-specific code to help maximize compatibility.
Not much of a guide, but these are things that have really helped me out in the past few days. The purpose of this blog was mostly just to plug jsFiddle. Seriously, it's awesome.

Friday, November 18, 2011

Cross-platform communication using Google's Protocol Buffers

NOTE: The C++ portion of this blog entry is incorrect. I've made some pretty stupid mistakes. These are discussed in a newer blog entry, which can be found here.

In this entry I will be discussing using Google's message format, Protocol Buffers, to communicate between a Java client and a C++ server using TCP sockets.

I came across protobuf in my search for a good means of communicating over the network between apps that may not be written in the same language. I wanted an Android phone, an iPhone, or even just a laptop to be able to communicate with the same server program. I feel like this is an increasingly desirable feature for mobile apps, so I'm going to regurgitate the information that I compiled on my search.

The way protocol buffers works is this: You define your message (data types and fields) in protobuf's own language. Then, once you have a properly formed message with all of the fields you need, you find a compiler for your language. Google provides official compilers for C++, Java, and Python. There is also a huge list of 3rd party compilers for many other languages (pretty much any one you can think of, including Objective C for you iPhone guys!).

Then you run the protobuf message through the compiler, and the compiler generates a library (source code/headers) for you to use that includes the message object, parsers, getters and setters, serializers and deserializers, and many other nifty little things that you would normally have to painstakingly code out for your own message. You "include" this in your program, and you're good to go!

Another advantage of protobuf is that Google encodes the messages in to their own binary format rather than ASCII, so the messages are a lot smaller than a message sent via JSON or XML.

I found an unsatisfactory amount of stuff on the internet about using protobuf across platforms. In my case, I wanted to know how to send a message from Java -> C++, and from C++ -> Java. So, I needed to know how to send and receive a message on both sides via TCP.

Here is a code example of a Java client sending a protobuf message to a C++ server, and the C++ server replying with another protobuf message.

Note: I am using Java NIO because it's just way easier to deal with than Streams, and it's more efficient.

Java Send

 //set up socket
 SocketChannel serverSocket;;
 serverSocket.connect(new InetSocketAddress(servIP,servPort));
 //create BAOS for protobuf
 ByteArrayOutputStream baos=new ByteArrayOutputStream();
 //mClientDetails is a protobuf message object, dump it to the BAOS

 //copy the message to a bytebuffer
 ByteBuffer socketBuffer=ByteBuffer.wrap(baos.toByteArray());

 //keep sending until the buffer is empty

C++ Receive

    //set up server socket
    sockaddr_in *sa=(sockaddr_in *)malloc(sizeof(struct sockaddr_in));
    memset(sa, 0, sizeof(struct sockaddr_in));
    sa->sin_family = AF_INET;
    sa->sin_addr.s_addr = htonl(INADDR_ANY);
    sa->sin_port = htons(port);
    int reuse=1;
    setsockopt(serverSock, IPPROTO_TCP, SO_REUSEADDR, &reuse, sizeof(reuse));

    //bind socket to port, listen
    bind(serverSock, (sockaddr *)sa, sizeof(*sa));
    listen(serverSock, 1);

    //create protobuf object
    protobuf::ClientDetails client;       

    //accept a client connection
    sockaddr_in *clientAddr;
    long unsigned int caSize=sizeof(clientAddr);
    int clientSock=accept(serverSock, (struct sockaddr *)&clientAddr, (socklen_t *)&caSize);

    //receive message from the client, where BUFFER_SIZE is large enough to contain your message
    int received=recv(clientSock, buffer, BUFFER_SIZE, 0);

    //read varint delimited protobuf object in to buffer
    //there's no method to do this in the C++ library so here's the workaround
    google::protobuf::io::ArrayInputStream arrayIn(buffer, received);
    google::protobuf::io::CodedInputStream codedIn(&arrayIn);
    google::protobuf::uint32 size;
    google::protobuf::io::CodedInputStream::Limit msgLimit = codedIn.PushLimit(size);

C++ Send

    //already set up a message object called serverAck
    //make a buffer that can hold message + room for a 32bit delimiter
    int ackSize=serverAck.ByteSize()+4;
    char* ackBuf=new char[ackSize];
    //write varint delimiter to buffer
    google::protobuf::io::ArrayOutputStream arrayOut(ackBuf, ackSize);
    google::protobuf::io::CodedOutputStream codedOut(&arrayOut);

    //write protobuf ack to buffer

    //send buffer to client
    send(clientSock, ackBuf, ackSize, 0);

Java Receive

//copy message byte array from socket buffer
byte[] ackBuf = new byte[socketBuffer.remaining()];

//create ByteArrayInputStream from byte[] (this is what protobuf wants)
ByteArrayInputStream ackStream=new ByteArrayInputStream(ackBuf);

//parse message
ServerAck serverAck=ServerAck.parseDelimitedFrom(ackStream);


For further reading on implementing protobuf, I recommend taking a look at Google's tutorials.