Java Socket Detailed Introduction _java

Returns the local host name and IP address;
InetAddress i = Inetaddress.getlocalhost ();
I.gethostaddress ();//ip
I.getaddress ()//???

Acquiring computer related information through computer name;
InetAddress i = inetaddress.getbyname ("livingstone-pc");

Get host-related information by domain name
InetAddress Ibaidu = Inetaddress.getbyname ("www.baidu.com");

URL url = new URL ("http://localhost:8080/demo.html");
Url.gethost ();

Tcp:

Socket (client):
When an object is established, it is possible to connect to the specified host, because TCP is connection-oriented, so when the socket service is established, there must be a server presence and the connection is successful and connected
After the data transmission in the channel;
Create the socket service for the client, specifying the target host and port;
Socket s = new socket ("CJ-PC", 10003);
In order to send data, the output stream in the socket stream should be obtained;
OutputStream out = S.getoutputstream ();
PrintWriter out = new PrintWriter (S.getoutputstream (), true); Out.println ("Hello");
Out.write ("Hello". GetBytes ());

Take back Send Message
InputStream in = S.getinputstream ();
byte[] Bufin = new byte[1024];
int num = In.read (bufin);
System.out.println (New String (bufin, 0, num));

S.close ();//Stream object in encapsulated in socket, automatically close stream object;

ServerSocket (service side):
Set up the socket service on the service side, ServerSocket and monitor a port;
Gets the client object that is connected, through the object's Accept method, waits (blocking) without a connection:
If the client sends data, the server will use the corresponding client object's read stream to obtain the data from the client;
ServerSocket ss = new ServerSocket (10003);

ServerSocket (int port,int backlog); Backlog is the maximum number of connections;
Socket s = ss.accept ();
InputStream in = S.getinputstream ();

byte[] buf = new byte[2014];
int len = In.read (BUF);

String rec = new String (buf, 0, Len);
SYSTEM.OUT.PRINTLN (REC);

Loopback message
OutputStream out = S.getoutputstream ();
Out.write ("Received". GetBytes ());

S.close ()//server will automatically shut down the client;
(1) Client:
Establish a socket service that specifies the host and port to be connected;
Gets the output stream in the socket stream, writes the data to the stream, and sends it to the server via the network;
Gets the input stream in the socket stream, obtains the data of the server feedback and closes the client resource;

Udp:

Datagramsocket: Send a piece of text data through UDP transmission mode;
Send:
Create a UDP service, create a Datagramsocket object and give a commodity number;
Datagramsocket socket = new Datagramsocket (8888);

Determine the data and encapsulate it into a packet, Datagrampacket (Specify the port number of the destination machine);
byte[] buf = "udp I ' m coming". GetBytes ();
Datagrampacket DP = new Datagrampacket (buf, Buf.length,
Inetaddress.getbyname ("Machine-name"), 10086);
Send
Socket.send (DP);
Close
Socket.close ();
Receive:
Define the Udpsocket service. Usually listens to a port, in fact, to the receiving network application to define the digital ID;
Datagramsocket socket = new Datagramsocket (10086);
while (true) {//purpose is to continuously monitor
byte[] buf = new byte[1024];
Defines a packet for storing data;
Datagrampacket DP = new Datagrampacket (buf, buf.length);
The received data is stored in the packet through the receive method of the service;
Socket.receive (DP),//blocking method, no data on the card die here;
Obtaining the data by means of a packet;
String IP = dp.getaddress (). gethostaddress ();
String data = new String (Dp.getdata (), 0, Dp.getlength ());
int port = Dp.getport ();
}

File Upload:

Socket s = new socket ("Machine-name", 10005);
OutputStream out = S.getoutputstream ();
FileInputStream fis = new FileInputStream ("awf.jpg");
byte[] buf = new byte[1024];
int len = 0;
while (len = Fis.read (buf))!=-1) {
Out.write (buf, 0, Len);
}
Stop sending data
S.shutdownoutput ();

ServerSocket ss = new ServerSocket (10005);//ss.accept () method has blocking effect;
A separate thread can be established for each socket obtained by the Accept () method;