catalogue
1, There are two main problems in network programming:
2, Two elements in network programming:
3, Communication element 1: IP and port number
4, Realize TCP network programming
Example 2: the client sends a file to the server, which saves the file locally.
5, Network programming of UDP protocol
6, URL: Uniform Resource Locator
1, There are two main problems in network programming:
1. How to accurately locate one or more hosts on the network; Locate a specific application on the host 2. How to transmit data reliably and efficiently after finding the host
2, Two elements in network programming:
1. Corresponding question 1: IP and port number 2. Corresponding question 2: provide network communication protocol: TCP/IP reference model (application layer, transmission layer, network layer, data link layer, physical layer)
3, Communication element 1: IP and port number
1.IP: uniquely identifies the computer (communication entity) on the Internet
2. Use InetAddress class to represent IP in java
3.Ip Classification: IPv4 and IPv6; World Wide Web and local area network
4. Domain name: www.baidu.com com
5. Local loop address: 127.0.0.1 corresponds to: localhost
6. How to instantiate InetAddress: two methods: getbyname (string host), getlocalhost();
Two common methods: getHostName() / getHostAddress()
7. Port number: the process running on the computer. Requirements: different processes have different port numbers
Range: specified as a 16 bit integer 0 ~ 65535.
8. The combination of port number and IP address leads to a network Socket: Socket
4, Realize TCP network programming
Direct code display
Example 1: the client sends information to the server, which displays the information on the console.
public class TCPTest {
//client
@Test
public void client() {
Socket socket = null;
OutputStream ops = null;
try {
//1. Create a Socket object to indicate the ip and port number of the server
InetAddress inet = InetAddress.getByName("127.0.0.1");
socket = new Socket(inet, 666);
//2. Get an output stream
ops = socket.getOutputStream();
//3. Write out data with output stream
ops.write("I'm a client".getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
//4. Resource shutdown: (stream and socket)
if (ops != null) {
try {
ops.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
//Server
@Test
public void server() {
ServerSocket serverSocket = null;
InputStreamReader isr = null;
try {
//1. Create a ServerSocket on the server side and indicate its own port number
serverSocket = new ServerSocket(666);
//2. The call to accept() indicates that the socket of the client can be received
Socket accept = serverSocket.accept();
//3. Get an input stream
//If there are Chinese characters, the bytes may be garbled So change the conversion flow
isr = new InputStreamReader(accept.getInputStream());
//4. Read data from input stream
char[] c = new char[100];
int len;
while ((len = isr.read(c)) != -1) {
String s = new String(c, 0, len);
System.out.println(s);
//Other needs
System.out.println("Received from client:" + serverSocket.getInetAddress().getHostName() + "Message from");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
//5. Close resources (streams and socket s)
if (isr != null) {
try {
isr.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (serverSocket != null) {
try {
serverSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
Example 2: the client sends a file to the server, which saves the file locally.
public class TCPTest2 {
@Test
public void client(){
Socket socket = null;
OutputStream os = null;
FileInputStream fis = null;
try {
socket = new Socket(InetAddress.getByName("127.0.0.1"),622);
os = socket.getOutputStream();
fis = new FileInputStream(new File("lizhi.png"));
byte[] b = new byte[1024];
int len;
while ((len = fis.read(b)) != -1){
os.write(b,0,len);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fis != null){
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (os != null){
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
@Test
public void server(){
ServerSocket ss = null;
InputStream inputStream = null;
FileOutputStream fos = null;
Socket accept = null;
try {
ss = new ServerSocket(622);
accept = ss.accept();
inputStream = accept.getInputStream();
fos = new FileOutputStream(new File("Self-Improvement.png"));
byte[] b = new byte[1024];
int len ;
while ((len = inputStream.read(b)) != -1){
fos.write(b,0,len);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (fos != null)
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
if (inputStream != null)
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
if (accept != null)
accept.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
if (ss != null)
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Example 3: send files from the client to the server, and the server saves them locally. And return the successful sending to the client. And close the corresponding connection.
public class TCPTest3 {
@Test
public void client() {
Socket socket = null;
OutputStream os = null;
FileInputStream fis = null;
try {
socket = new Socket(InetAddress.getByName("127.0.0.1"), 622);
os = socket.getOutputStream();
fis = new FileInputStream(new File("lizhi.png"));
byte[] b = new byte[1024];
int len;
while ((len = fis.read(b)) != -1) {
os.write(b, 0, len);
}
// Here, the client must manually stop the execution of read() because it is a blocking method and does not know when to stop.
socket.shutdownOutput();
// Here you need to receive messages from the server
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
char[] chars = new char[5];
int len1;
while ((len1 = isr.read(chars)) != -1) {
String s = new String(chars, 0, len1);
System.out.print(s);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fis != null) {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (os != null) {
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
@Test
public void server() {
ServerSocket ss = null;
InputStream inputStream = null;
FileOutputStream fos = null;
Socket accept = null;
try {
ss = new ServerSocket(622);
accept = ss.accept();
inputStream = accept.getInputStream();
fos = new FileOutputStream(new File("Self-Improvement.png"));
byte[] b = new byte[1024];
int len;
while ((len = inputStream.read(b)) != -1) {
fos.write(b, 0, len);
}
// Here you need to give feedback to the client
OutputStream os = accept.getOutputStream();
os.write("Your message was sent successfully".getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (fos != null)
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
if (inputStream != null)
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
if (accept != null)
accept.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
if (ss != null)
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
5, Network programming of UDP protocol
public class UDPTest {
//Sender
@Test
public void sender() {
DatagramSocket Socket = null;
try {
Socket = new DatagramSocket();
String s = new String("I am udp From");
byte[] bytes = s.getBytes();
InetAddress inet = InetAddress.getByName("127.0.0.1");
DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length, inet, 666);
Socket.send(packet);
} catch (IOException e) {
e.printStackTrace();
} finally {
Socket.close();
}
}
//receiving end
@Test
public void receiver() {
DatagramSocket datagramSocket = null;
try {
datagramSocket = new DatagramSocket(666);
byte[] bytes = new byte[100];
DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length);
datagramSocket.receive(packet);
System.out.println(new String(packet.getData(), 0, packet.getLength()));
} catch (IOException e) {
e.printStackTrace();
} finally {
datagramSocket.close();
}
}
}6, URL: Uniform Resource Locator
Five basic structures of URL * http://localhost:8080/examples/beauty.jpg?username=Tom *Protocol host name port number resource address parameter list