catalogue
1, Network programming for TCP
2. Example 2: the client sends the file to the server, and the server saves the file locally
1, Network programming for TCP
1. Example 1: the client sends information to the server, and the server displays the data on the console
① Client
@Test
public void client() {
Socket socket = null;
OutputStream os = 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,8899);
//2. Obtain an output stream for outputting data
os = socket.getOutputStream();
//3. Write data
os.write("Hello, this is the client".getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
//4. Closure of resources
if(os != null){
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}② Server
@Test
public void server(){
ServerSocket ss = null;
Socket socket = null;
InputStream is = null;
ByteArrayOutputStream baos = null;
try {
//1. Create a ServerSocket on the server side and indicate its own port number
ss = new ServerSocket(8899);
//2. Call accept() to receive the socket from the client
socket = ss.accept();
//3. Get input stream
is = socket.getInputStream();
//It is not recommended to write like this. There may be garbled code
// byte[] buffer = new byte[1024];
// int len;
// while ((len = is.read(buffer)) != -1){
// String str = new String(buffer,0,len);
// System.out.println(str);
// }
//4. Read the data in the input stream
baos = new ByteArrayOutputStream();
byte[] buffer = new byte[20];
int len;
while ((len = is.read(buffer)) != -1){
baos.write(buffer,0,len);
}
System.out.println(baos.toString());
} catch (IOException e) {
e.printStackTrace();
} finally {
//5. Close resources
if(baos != null){
try {
baos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(is != null){
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(socket != null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(ss != null){
try {
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}2. Example 2: the client sends the file to the server, and the server saves the file locally
① Client
@Test
public void client(){
Socket socket = null;
OutputStream os = null;
FileInputStream fis = null;
try {
socket = new Socket(InetAddress.getByName("127.0.0.1"),9090);
os = socket.getOutputStream();
fis = new FileInputStream(new File("2390865548.jpg"));
byte[] buffer = new byte[1024];
int len;
while ((len = fis.read(buffer)) != -1){
os.write(buffer,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();
}
}
}
}② Server
@Test
public void server(){
ServerSocket ss = null;
Socket socket = null;
InputStream is = null;
FileOutputStream fos = null;
try {
ss = new ServerSocket(9090);
socket = ss.accept();
is = socket.getInputStream();
fos = new FileOutputStream("2390865548(1).jpg");
byte[] buffer = new byte[1024];
int len;
while ((len = is.read(buffer)) != -1){
fos.write(buffer,0,len);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if(fos != null){
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(is != null){
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(socket != null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(ss != null){
try {
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}3. Example 3: Send a file from the client to the server, the server saves it locally, returns "send successfully" to the client, and closes the corresponding connection
@Test
public void client(){
Socket socket = null;
OutputStream os = null;
FileInputStream fis = null;
try {
socket = new Socket(InetAddress.getByName("127.0.0.1"),8080);
os = socket.getOutputStream();
fis = new FileInputStream(new File("2390865548.jpg"));
byte[] buffer = new byte[1024];
int len;
while ((len = fis.read(buffer)) != -1){
os.write(buffer,0,len);
}
socket.shutdownOutput();
//Receive data from the server and display it on the console
InputStream is = socket.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer2 = new byte[1024];
int len2;
while ((len2 = is.read(buffer2)) != -1){
baos.write(buffer2,0,len2);
}
System.out.println(baos.toString());
} 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();
}
// if(baos != null){
// baos.close();
// }
}
}
}
@Test
public void server(){
ServerSocket ss = null;
Socket socket = null;
InputStream is = null;
FileOutputStream fos = null;
try {
ss = new ServerSocket(8080);
socket = ss.accept();
is = socket.getInputStream();
fos = new FileOutputStream("2390865548(2).jpg");
byte[] buffer = new byte[1024];
int len;
while ((len = is.read(buffer)) != -1){
fos.write(buffer,0,len);
}
//The server gives feedback to the client
OutputStream os = socket.getOutputStream();
os.write("Hello, the photo has been received!".getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
if(fos != null){
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(is != null){
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(socket != null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(ss != null){
try {
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
// if (os != null){
// os.close();
// }
}
}2, Client server
1. Client
① Browser
② Custom
2. Server
① Tomcat server
② Custom
3, UDP network programming
1.UDP network communication
- Classes datagram socket and datagram packet implement network programs based on UDP protocol.
- UDP datagrams are sent and received through datagram socket. The system does not guarantee that UDP datagrams can be safely sent to the destination, nor can it determine when they can arrive.
- The datagram packet object encapsulates UDP datagrams, which contain the IP address and port number of the sender and the lIP address and port number of the receiver.
- Each datagram in UDP protocol gives complete address information, so there is no need to establish a connection between the sender and the receiver. It's like sending an express package.
2. Sender
@Test
public void send() throws IOException {
DatagramSocket socket = new DatagramSocket();
String str = "I am UDP Sent by~";
byte[] data = str.getBytes(StandardCharsets.UTF_8);
InetAddress inet = InetAddress.getLocalHost();
DatagramPacket packet = new DatagramPacket(data,0,data.length,inet,9090);
socket.send(packet);
socket.close();
}3. Receiving end
@Test
public void receiver() throws IOException {
DatagramSocket socket = new DatagramSocket(9090);
byte[] buffer = new byte[20];
DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length)
socket.receive(packet);
System.out.println(new String(packet.getData(),0,packet.getLength()));
socket.close();
}