Socket Programming

Posted 2020-10-07 木子楼

| There are two ways to store this value.

• Little Endian.（低位优先）
• Big Endian.（高位优先）

| The complete Client and Server interaction.

| The simplest way to write a concurrent server under Unix is to fork a child process to handle each client separately.

| Socket Type

• Stream Sockets（TCP）[most commonly used]
• Datagram Sockets （UDP）[most commonly used]
• Raw Sockets (Raw Sockets are not intended for the general user; they have been provided mainly for those interested in developing new communication protocols, of for gaining access to some of the more cryptic facilities of an existing protocol.) [rarely used]
• Sequenced Packet Socket [rarely used]

| Where is socket used?
A Unix socket is used in a client-server application framework.

| In Unix, every I/O action is done by writing or reading a file descriptor.

| Socket allow communication between two different processes on the same or different machines.

| Unix Socket
https://www.tutorialspoint.com/unix_sockets/

---

| Connection-oriented socket (TCP)

| Connectionless socket (UDP)

| 你一言我一语(Java语言实现)：

//: MyServer.java
import java.io.*;
import java.net.*;

public class MyServer{
  public static void main(String[]args) {
    try {
      ServerSocket ss = new ServerSocket(6666);
      Socket s = ss.accept();

      DataInputStream dis = new DataInputStream(s.getInputStream());
      DataOutputStream dos = new DataOutputStream(s.getOutputStream());

      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      String str = "";
      while (!str.equals("stop")) {

        str = (String)dis.readUTF();
        System.out.println("[client] " + str);

        str = br.readLine();
        System.out.println("[server] " + str);
        dos.writeUTF(str);
        dos.flush();

      }

      s.close();
      ss.close();

    } catch (Exception e){
      System.out.println(e);
    }
  }
}

//: MyClient.java
import java.io.*;
import java.net.*;

public class MyClient {
  public static void main (String []args) {
    try {
      Socket s = new Socket("localhost", 6666);
      DataOutputStream dos = new DataOutputStream(s.getOutputStream());
      DataInputStream dis = new DataInputStream(s.getInputStream());

      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String str = "";

      while(!str.equals("stop")) {
        str = br.readLine();
        dos.writeUTF(str);
        dos.flush();
        System.out.println("[client] " + str);

        System.out.println("[server] " + dis.readUTF());
      }

      dos.close();
      s.close();
    } catch (Exception e) {
      System.out.println(e);
    }

  }
}

• Java Socket Programming
• Java DatagramSocket and DatagramPacket
• Socket programming笔记

来自为知笔记(Wiz)