Socket Simple Foundation (1)

For sockets, we used to use them simply, without systematic study. This time, there is a good teaching material document, review it from the beginning, and deepen the understanding of sockets.
First, a most basic socket application, a simple chat.

//create server
ServerSocket server = new ServerSocket(9090);
//After waiting for the client connection to enter, after entering, generate a Socket object
java.net.Socket client=server.accept();
System.out.println ("Incoming "+client.getRemoteSocketAddress());
//Note: server.accept() is a blocking method, which is blocked on this call. Only when a socket client is connected, this method will have a return value and return the client's socket object, which is the client at this time. The client and server are connected.
//Get the input and output stream after connecting to the client
OutputStream ops = client.getOutputStream();
InputStream ips = client.getInputStream();
//Note: Write data to the input stream and send it to the client, and write data to the output stream and send it to the server.
//Send byte data experiment
String s = "Welcome" + username + "come to chat room\r\n";
byte[] b = s.getBytes();
ops.write(b);
ops.flush();
String str = readString(ips);
while (!str.equals("over")) {
	System.out.println("Server received: " + str);
	ChatTools.sendMsg(this.user,str);
	str = readString(ips);
}
String n = "Call ended";
ops.write(n.getBytes());
ops.flush();
//Close the connection to the client
client.close;

readString is also a blocking method, mainly in ips.read(), this method will have a return value only when the client inputs a character.

private String readString(InputStream ips) throws IOException {
		StringBuffer sb = new StringBuffer();
		char c = 0;
        //until carriage return is a string
		while (c != 13) {
            //delete
			if (c == 8) {
				sb.deleteCharAt(sb.length() - 1);
				c = (char) ips.read();
			} else {
				sb.append(c);
				c = (char) ips.read();
			}
		}
		String str = sb.toString().trim();
		return str;
	}

At this time, you can enter telnet locahost 9090 in the command line to connect to the server