TCP协议是一个有连接可靠地协议。
TCP编程的核心思路 开发服务器端
ServerSocket ss=new ServerSocket(9000)
ss.accept();
public class TcpServer {
public static void main(String[] args) {
try {
ServerSocket ss= new ServerSocket (9000); //创建SocketServer对象,并绑定端口
Socket s=ss.accept();
BufferedReader br= new BufferedReader( new InputStreamReader(s.getInputStream())); //调用getInputStream方法，进行I/O操作
String str=br.readLine();
System. out .println( "接收的数据为：" +str);
s.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class TcpServer02 {
public static void main(String[] args) {
try {
ServerSocket ss= new ServerSocket(9000);//创建SocketServer对象,并绑定端口
Socket s=ss.accept();
BufferedReader br= new BufferedReader(new InputStreamReader(s.getInputStream()));//调用getInputStream方法，进行I/O操作
String str=br.readLine();
System. out.println("接收的数据为：" +str );
PrintWriter pw= new PrintWriter(s.getOutputStream());
pw.println( str+"from Server");
pw.flush();
s.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
开发客户端
Socket s=new Socket("150.236.56.101",9000);
public class TcpClient {
public static void main(String[] args) {
try {
Socket s= new Socket("localhost" ,9000);//创建Socket对象，并连接服务器
PrintWriter pw= new PrintWriter(s.getOutputStream());//调用getOutputStream方法，进行I/O操作
pw.println( "Hello world!");
pw.flush(); //将缓冲区里的数据向外发出
s.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class TcpClient02 {
public static void main(String[] args) {
try {
Socket s= new Socket("localhost" ,9000);//创建Socket对象，并连接服务器
PrintWriter pw= new PrintWriter(s.getOutputStream());//调用getOutputStream方法，进行I/O操作
pw.println( "Hello world!");
pw.flush(); //将缓冲区里的数据向外发出
BufferedReader br= new BufferedReader(new InputStreamReader(s.getInputStream()));
String str=br.readLine();
System. out.println("接收服务器返回信息：" +str);
s.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
以上程序存在的问题，服务器只能运行一次
while(true){
调用accept()方法
调用getXXXStream方法，进行I/O操作
关闭Socket
}
像以上那样加入一个死循环，也不能达到目的，所以此时可以运用线程来操作
public class ServerThread extends Thread{
Socket s ;
public ServerThread(Socket s) {
this . s =s;
}
public void run() { //实现run()方法
try {
BufferedReader br= new BufferedReader( new InputStreamReader( s .getInputStream())); //调用getInputStream方法，进行I/O操作
String str=br.readLine();
System. out .println( "接收的数据为：" +str);
PrintWriter pw= new PrintWriter( s .getOutputStream());
pw.println(str+ "from Server" );
pw.flush();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
s .close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public class TcpServer03 {
public static void main(String[] args) throws IOException {
ServerSocket ss= new ServerSocket(9000);
while(true ){
Socket s=ss.accept();
Thread st= new ServerThread(s);
st.start();
}
}
}
UDP:无连接，不可靠(应用：网络视频聊天)
UDP编程
java.net.DatagramSocket
java.net.DatagramPacket
UDP编程的核心思路
服务器 DatagramSocket socket=new DatagramSocket(9000)
客户端 DatagramSocket socket=new DatagramSocket()
DatagramPacket
DatagramPacket(byte[] buf,int,length)DatagramPacket(byte[] buf,int,length,SocketAddress)getAddress()/getSockAddress()/getPort()/getLength()setAddress()/setSockAddress()/setPort()/setLength()
public class UdpClient {
public static void main(String[] args) throws IOException {
DatagramSocket socket= new DatagramSocket();
String str= "Hello World!";
byte[] buf=str.getBytes();
DatagramPacket packet= new DatagramPacket(buf,0,buf.length ,new InetSocketAddress("localhost" ,9000));
socket.send(packet);
socket.close();
}
}
public class UdpServer {
public static void main(String[] args) throws IOException {
DatagramSocket socket= new DatagramSocket(9000);
byte[] buf=new byte[100];
DatagramPacket paper= new DatagramPacket(buf,0,buf.length );
socket.receive(paper);
String str=new String(buf,0,paper.getLength());
System. out.println(str);
socket.close();
}
}
URL概念（统一资源定位符 ）
URL组成
协议名：//主机名（或者IP地址）：端口号/资源
如：http://localhost:8080/web/a.jpg;
URL编程
URL
URLConnection
public class URLTest {
public static void main(String[] args) throws IOException {
URL url= new URL("http://www.Oracle.com" );
URLConnection conn=url.openConnection();
InputStream in=conn.getInputStream();
BufferedReader br= new BufferedReader(new InputStreamReader(in));
String line= null;
while((line=br.readLine())!=null){
System. out.println(line);
}
br.close();
}
}