sockets套接字入门


备注

本节概述了套接字是什么,以及开发人员可能想要使用它的原因。

它还应该提到套接字中的任何大型主题,并链接到相关主题。由于套接字文档是新的,您可能需要创建这些相关主题的初始版本。

创建未连接的套接字,尝试连接到它并检查是否建立了连接

 public class ConnectSocketExample {

    private int HTTP_PORT = 80;

    /**
     * example method to create unconnected socket
     * then connect to it
     * at end return connected socket
     *
     * @param httpHostName - endpoint host name fot socket connection
     * @throws IOException - if the socket is already connected or an error occurs while connecting.
     */
    protected Socket connectSocket(String httpHostName) throws IOException {
        // define local variable for socket and create unconnected socket
        Socket socket = new Socket();
        //  create iNet address for socket
        InetSocketAddress inetSocketAddress = new InetSocketAddress(httpHostName, HTTP_PORT);
        // connect socket to inet address (end point )
        socket.connect(inetSocketAddress);
        // return connected socket for later use 
        return socket;
    }
    
    /** 
     * public method for try to create connected to goole.com http port socket 
     * and with check and system out print if this try was successful
     **/
    public void createAndCheckIfConnected() {
        try {
            Socket connectedSocket = connectSocket("google.com");
            boolean connected = connectedSocket.isConnected();
            System.out.print("Socket is:" + (!connected ? " not" : "" +  " connected"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}
 

如何实例化套接字类对象

可以以各种方式实现套接字的实例化。

  1. 通过2行声明和实例化:

    首先,我们需要定义一个包含Socket类对象的变量:

    Socket socket;
     

    然后我们可以创建一个Socket类对象:

    socket = new Socket();
     
  2. 我们还可以进行一行定义和实例化:

    Socket  socket = new Socket();
     

两种方式都会创建一个未连接的套接字。

我们可以使用其他参数化构造函数来实例化连接或未连接的套接字类对象:

有关详细信息,请参阅类doc规范:

https://docs.oracle.com/javase/7/docs/api/java/net/Socket.html

写入socket一个简单的http get请求,并转储响应

/** 
 * we reuse a class written in example:
 * http://stackoverflow.com/documentation/sockets/2876/introduction-to-sockets#t=201607262114505531351
 * pleas to familiar with it first to continue with this one 
 **/
public class WriteToSocketExample extends ConnectSocketExample {

    private String CRLF = "\r\n"; // line termination (separator)

    /**
     * write a simple http get request to socket
     * @param host - host to establish a connection
     *               (http server - see ConnectSocketExample HTTP_PORT )
     * @param path - path to file ( in this case a url location - part used in browser after host)
     * @return a  connected socket with filled in raw get request
     * @throws IOException - see ConnectSocketExample.connectSocket(host);
     */
    protected Socket writeGetToSocket(String host, String path) throws IOException {
        // create simple http raw get request for host/path
        String rawHttpGetRequest = "GET "+ path +" HTTP/1.1 " + CRLF  // request line
                + "Host: "+ host + CRLF
                + CRLF;
        // get bytes of this request using proper encodings
        byte[] bytesOfRequest = rawHttpGetRequest.getBytes(Charset.forName("UTF-8)"));
        // create & connect to socket
        Socket socket = connectSocket(host);
        // get socket output stream
        OutputStream outputStream = socket.getOutputStream();
        // write to the stream a get request we created
        outputStream.write(bytesOfRequest);
        // return socket with written get request
        return  socket;
    }

    /**
     * create, connect and write to socket simple http get request
     * then dump response of this request
     * @throws IOException
     */
    public void writeToSocketAndDumpResponse() throws IOException {
        // send request to http server for / page content
        Socket socket = writeGetToSocket("google.com", "/");
        // now we will read response from server
        InputStream inputStream = socket.getInputStream();
        // create a byte array buffer to read respons in chunks
        byte[] buffer = new byte[1024];
        // define a var to hold count of read bytes from stream
        int weRead;
        // read bytes from sockets till exhausted or read time out will occurred ( as we didn't add in raw get header Connection: close (default keep-alive)
        while ((weRead = inputStream.read(buffer)) != -1) {
            // print what we have read
            System.out.print(new String(buffer));
        }
    }
}