TCP
TCP在计网中的位置十分重要，很多协议的运行都是以TCP为基础来运行的，虽然TCP的开销比UDP开销大，但其实现的可靠性交付是一大特点，其还具有流量控制、拥塞控制等特性，在面试中也少不了谈其三次握手、四次挥手以及其他问题。
public class LengthCalculator extends Thread{
private Socket socket;
public LengthCalculator(Socket socket){
this.socket=socket;
}
@Override
public void run(){
try{
OutputStream os =socket.getOutputStream();
InputStream is =socket.getInputStream();
int ch=0;
byte[] buff =new byte[1024];
ch=is.read(buff);
String content =new String(buff,0,ch);
System.out.println(content);
os.write(String.valueOf(content.length()).getBytes());
is.close();
os.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class TCPClient {
public static void main(String[] args) throws IOException {
Socket socket=new Socket("127.0.0.1",65000);
OutputStream out = socket.getOutputStream();
InputStream in = socket.getInputStream();
out.write("Hello World!".getBytes());
int ch=0;
byte[] bytes=new byte[1024];
ch=in.read(bytes);
String content=new String(bytes,0,ch);
System.out.println("接收到内容content:"+content);
in.close();
out.close();
socket.close();
}
}
public class TCPServer {
public static void main(String[] args) throws IOException {
ServerSocket ss =new ServerSocket(65000);
while(true){
Socket socket=ss.accept();
new LengthCalculator(socket).start();
}
}
}
UDP
UDP是数据报传输协议，其可传输的大小取决于数据报的大小，不像TCP协议一样受到MTU最大传输的限制，也不用像TCP一样实现报文切片等特性进行传输，但UDP的主要传输速率取决于双方的带宽，且不提供可靠性交付。
public class UDPClient {
public static void main(String[] args) throws IOException {
DatagramSocket socket =new DatagramSocket();
byte[] buf ="hello world".getBytes();
//将IP封装为InetAddress对象
InetAddress address =InetAddress.getByName("127.0.0.1");
//将要发送数据封装成DatagramPacket对象，填写上ip地址与端口号
DatagramPacket packet =new DatagramPacket(buf,buf.length,address,65001);
socket.send(packet);
byte[] data =new byte[100];
//创建DatagramPacket对象来存储服务端发送的数据
DatagramPacket receivedPacket = new DatagramPacket(data,data.length);
socket.receive(receivedPacket);
//将数据取出来并打印
String content = new String(receivedPacket.getData(),0,receivedPacket.getLength());
System.out.println(content);
}
}
public class UDPServer {
public static void main(String[] args) throws IOException {
//服务端接收客户端发送的数据报
DatagramSocket socket =new DatagramSocket(65001);
//存储从客户端收到的内容
byte[] buff =new byte[100];
//接收客户端发送的内容，并将内容封装进DatagramPacket对象中
DatagramPacket packet =new DatagramPacket(buff,buff.length);
socket.receive(packet);
//从DatagramPacket中获取真正存储的数据
byte[] data =packet.getData();
//将数据从二进制转化为字符串形式
String content =new String(data,0,packet.getLength());
System.out.println(content);
//将要发送给客户端的数据换成二进制
byte[] sendedContent =String.valueOf(content.length()).getBytes();
//服务端给客户端发送数据报
//从DatagramPacket对象中获取到数据的来源地址与端口号
DatagramPacket packetToClient =new DatagramPacket(sendedContent,sendedContent.length,packet.getAddress(),packet.getPort());
socket.send(packetToClient);
}
}
