Java Socket网络编程
1. Ip地址，域名和端口号
JDK的java.net包中定义了与IP地址/域名有关的类
1.java.net.InetAddress
32位或128位无符号数字表示的IP地址。
2.java.net.Inet4Address
继承了InetAddress类，以32位无符号数字表示的IPv4地址。
3.java.net.Inet6Address
集成了InetAddress类，以128为无符号数字表示的IPv6地址。
public class TestInetAddress {
public static void main(String args[]){
try {
InetAddress ia = InetAddress.getLocalHost();
showInfo(ia);
ia = InetAddress.getByName("www.sina.com");
showInfo(ia);
} catch (UnknownHostException e) {
e.printStackTrace();
}
}
public static void showInfo(InetAddress ia){
String name = ia.getHostName();
String address = ia.getHostAddress();
print("name:" + name);
print("address:" + address);
}
public static void print(Object o){
System.out.println(o);
}
}
运行结果：
name:QQ-PC address:60.166.219.14 name:www.sina.com address:61.172.201.195
2. URL
URL(Uniform Resource Locator,统一资源定位器）用于表示Internet上资源的地址。
URL格式：<协议名><资源所在主机名>[:<端口号>]<资源名>
http://home.netscape.com/home/welcome.html
java.net包定义了对应的URL类，常用方法如下：
public URL(String spec)
public final InputStream openStream() throws IOException
public class URLReader {
public static void main(String args[]){
URL url;
try {
url = new URL("http://www.baidu.com");
BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
String s = reader.readLine();
while(null != s){
System.out.println(s);
s = reader.readLine();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
运行结果：
<!doctype html><html><head><meta http-equiv="Content-Type" content="text/html;charset=gb2312"><title>百度一下，你就知道
3 Socket编程
两个进程间可以通过一个双向的网络通信连接实现数据交换，这种通信链路的端点被称为“套接字”（Socket） 。
Socket通常用来实现Client-Server连接。
建立连接时所需的寻址信息
1.远程计算机的机器名或IP地址
2.试图连接的端口号（Port number)
java.net包中定义的两个类Socket和ServerSocket，分别用来实现双向连接的client和server端。在Socket和ServerSocket类常用的构造方法如下：
Socket(InetAddress address,int port) throws IOException;
Socket(String host,int port) throws IOException
ServerSocket(int port) throws IOException
ServerSocket(int port,int backlog) throws IOException
Socket网络编程可分为四个基本步骤：
1. 建立网络连接。
2. 打开连接到Socket
3. 通过打开的I/O流进行数据读/写操作
4. 关闭已打开的I/O流和Socket
Server:
public class TestServer {
public static void main(String args[]){
ServerSocket server;
try {
server = new ServerSocket(8888);
System.out.println("Server is running!");
while(true){
Socket s1 = server.accept();//如果没有客户端进来，将会处于阻塞状态
OutputStream os = s1.getOutputStream();
DataOutputStream dos = new DataOutputStream(os);
dos.writeUTF("Hi,Client Address is:" + s1.getInetAddress() + "\tClient port:" + s1.getPort());
dos.writeUTF("byte！");
dos.close();
s1.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Client:
public class TestClient {
public static void main(String args[]) {
Socket client;
try {
client = new Socket("127.0.0.1", 8888);
InputStream is = client.getInputStream();
DataInputStream dis = new DataInputStream(is);
print(dis.readUTF());
print(dis.readUTF());
dis.close();
client.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void print(Object o) {
System.out.println(o);
}
}
应该先运行Server，然后在运行Client。
简单的聊天程序 ：
Server：
public class TestServerChat {
public static void main(String args[]){
try {
ServerSocket server = new ServerSocket(8888);
Socket s1 = server.accept();
OutputStream os = s1.getOutputStream();
DataOutputStream dos = new DataOutputStream(os);
InputStream is = s1.getInputStream();
DataInputStream dis = new DataInputStream(is);
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String info;
while(true){
info = dis.readUTF();
print("Client：" + info);
if(info.equals("byte")){
break;
}
info = reader.readLine();
dos.writeUTF(info);
if(info.equals("byte")){
break;
}
}
dis.close();
reader.close();
server.close();
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void print(Object o){
System.out.println(o);
}
}
Client：
public class TestClientChat {
public static void main(String args[]) {
Socket client;
try {
client = new Socket("127.0.0.1", 8888);
InputStream is = client.getInputStream();
DataInputStream dis = new DataInputStream(is);
OutputStream os = client.getOutputStream();
DataOutputStream dos = new DataOutputStream(os);
BufferedReader reader = new BufferedReader(new InputStreamReader(
System.in));
String info;
while (true) {
info = reader.readLine();
dos.writeUTF(info);
if (info.equals("byte")) {
break;
}
info = dis.readUTF();
print("Server：" + info);
if (info.equals("byte")) {
break;
}
}
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void print(Object o) {
System.out.println(o);
}
}
此简易聊天程序有很大的局限性，仅可以一人一句。