[MUSIC] So remember that, typically, the Internet is used in this client-server relationship, not always, but that's what we're assuming here. So client-server relationship, what this means is that the server sits there, and waits for connections, right. Like a web server, it sits there, and has some kind of service it's providing. Like a web server, it provides a web page. It provides web pages. So it sits there on the network, listening and waiting for connections, for people to request something. Then a client does the requesting. So a client connects to the server and request some service. Like request a web page, please give me a web page or something like that. So we're assuming this client server relationship. Our Ethernet shield can act as a client or a server. So right now we are going to talk about using the Ethernet shield as a client. When you do that, first thing you do is you have to create a client object, okay. So Ethernet Client is the name of this class. You say EthernetClient client, and that creates a client object. You need that if you wanna act as a client. So you create the client object, then you need to connect to a server, right. If you're a client, you're gonna wanna connect to a server to get some service from. So you can do that, we're showing two ways of doing it, basically you're calling this function called client.connect. Now client.connect, it takes two arguments. The first argument, well actually we showed two calls right here. The first call, its two arguments are IP address and a port. So you gotta give the IP address and the port number as its two arguments and then it knows what machine to talk to. Or you can pass the two arguments of the domain name and the port. And, remember, using Domain Name Service, DNS, the domain name can automatically be translated into an IP address. So either way is fine. client.connect you can call it, give it an IP address and a port number and it makes a connection with a server. Now notice that line of code says result equals client.connect, result equals. So what that means is that client.connect is gonna return either a zero or a one. True or false. It returns a one if a connection is successfully made with a server. It returns a zero if it's not. And so then in your code you can say if result then da da da, right. So you can check to see if a connection was successfully made before you go on and start communicating. And client.stop that stops the connection. It ends the connection. So when you're done communicating, you just go client.stop and it closes the connection. So sending, receiving data. Now once you've made your connection, your client has made a connection to the server, you want to send data to the server and receive data from the server. So they have functions for that. client.print or client.println that sends data. print just sends the data and println sends the data and sends a carriage return at the end. That's common for sort of visible type data. If you're sending a line you just wanna put the carriage return in there automatically sometimes. So print, and println, client.print, client.println are used to send data. Now, and println is the character term. Data is a string, so if you wanna send strings you use print or println. Or an array of bytes which is also a string. Same thing. Now if you just wanna send raw data, it's not a string at all, then you call client.write and you just pass the value, whatever it is. If you send a byte values a byte you can send the client.write it'll send a byte. Now client.read is used to do the opposite. If want to read data. If you're trying to read data from the server. It calls client.read. No arguments and that just reads the next available byte. The next byte that's coming from the server. And it returns that. So data equals client.read, data is gonna end up equaling whatever byte was received from the server. Also, you can call client.available. Client.available lets you know if there is data waiting. So if client.available returns one, that means there is data waiting so you can call client.read. If client.available returns to zero, then there's no point in calling client.read because it will fail. Thank you. [MUSIC]
