<span>Java笔记--网络编程</span>
Java笔记--网络编程
一、 网络編程中有两个主要的问题:
- 如何准确地定位网络上一台或多台主机：定位主机上的特定的应用
- 到主机后如何可靠高效地进行数据传输
二、 网络编程的两个要素
- 对应问题一：IP和端口号
- 对应问题二：提供网络通信协议：TCP/IP参考模型
- 应用层
- 传输层
- 网路层
- 物理+数据链路层
通信要素一：IP和端口号
- IP：唯一的表示Internet上的计算机（通信实体）
- 在Java中使用InetAdress类代表IP
- IP分类：IPv4和IPv6；万维网和局域网
- 域名
- 本地回路地址：127.0.0.1 localhost
- 如何实例化InetAdress：两个方法：
- getByName(String host)
- getLocalHost()
- 获取域名，获取主机地址
- getHostName()
- getHostAdress()
public void test() {
try {
InetAddress inet1 = InetAddress.getByName("192.168.1.103");
InetAddress inet1_1 = InetAddress.getByName("tplogin.cn");
InetAddress inet2 = InetAddress.getByName("www.baidu.com");
InetAddress inet3 = InetAddress.getByName("localhost");
InetAddress inet3_1 = InetAddress.getLocalHost();
System.out.println(inet1);
System.out.println(inet1_1);
System.out.println(inet2);
System.out.println(inet3);
System.out.println(inet3_1);
System.out.println(inet2.getHostName());
System.out.println(inet2.getHostAddress());
} catch (UnknownHostException e) {
e.printStackTrace();
}
}
- 端口号：端口号标识正在计算机上运行运行的进程（程序）
- 不用的进程有不同的端口号
- 被规定为一个16位的整数0~65535。
- 端口分类：
- 公认端口：0~1023。被预先定义的服务通信占用（如：HTTP占用端口80，FTP占用端口21，Telnet占用端口23）
- 注册端口：1024-49151。分配给用户进程或应用程序。（如：Tomcat占用端口8080，MySQL占用端口3360，Oracle占用端口1521等）
- 动态/私有端口：49152-65535
- 端口号与IP地址的组合得出一个网络套接字：Socket
通信要素二：网络通信协议
TCP/IP协议簇
-
传输控制协议-------TCP
-
用户数据报协议---UDP
-
TCP协议:
➢ 使用TCP协议前，须先建立TCP连接，形成传输数据通道
➢ 传输前，采用“三次握手”方式，点对点通信，是可靠的
➢ TCP协议进行通信的两个应用进程:客户端、服务端。
➢ 在连接中可进行大数据量的传输
➢ 传输完毕，需释放已建立的连接，效率低 -
UDP协议
➢ 将数据、源、目的封装成数据包，不需要建立连接
➢ 将每个数据包的大小限制在64K内
➢发送不管对方是否准备好，接收方收到也不确认，故是不可靠的
➢可以广播发送
➢发送数据结束时无需释放资源，开销小，速度快
TCP的网络编程
客户端发送文本到服务端
@Test
//这是一个客户端的程序
public void client() {
Socket socket = null;
OutputStream os = null;
try {
InetAddress inet = InetAddress.getByName("192.168.1.103");
socket = new Socket(inet, 12356);
os = socket.getOutputStream();
os.write("我是WZL".getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
if (os != null) {
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
@Test
public void server() {
ServerSocket ss = null;
Socket sock = null;
InputStream is = null;
ByteArrayOutputStream baos = null;
try {
ss = new ServerSocket(12356);
sock = ss.accept();
is = sock.getInputStream();
//不建议这样直接去使用，遇到UTF-8的中文会乱码
//byte[] buffer = new byte[1024];
//int len;
//while ((len = is.read(buffer)) != -1){
// String str = new String(buffer);
// System.out.print(str);
//}
//使用ByteArrayOutputStream可以防止中文乱码问题
baos = new ByteArrayOutputStream();
byte[] buffer = new byte[5];
int len;
while ((len = is.read(buffer)) != -1){
baos.write(buffer, 0, len);
}
System.out.println(baos.toString());
System.out.println("收到了来自：" + sock.getInetAddress().getHostAddress() + "的消息");
} catch (IOException e) {
e.printStackTrace();
} finally {
if (baos != null) {
try {
baos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (is != null) {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (sock != null) {
try {
sock.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (ss != null) {
try {
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
客户端发送文件到服务端
@Test
public void client() {
Socket sock = null;
OutputStream os = null;
FileInputStream fis = null;
try {
InetAddress inet = InetAddress.getByName("192.168.1.103");
sock = new Socket(inet, 9090);
os = sock.getOutputStream();
fis = new FileInputStream(new File("IOTest/pic1.png"));
//传输文件
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 (sock != null) {
try {
sock.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
@Test
//文件传输服务端
public void server() {
ServerSocket ss = null;
Socket sock = null;
InputStream is = null;
FileOutputStream fos = null;
try {
ss = new ServerSocket(9090);
sock = ss.accept();
is = sock.getInputStream();
fos = new FileOutputStream(new File("~/IOTest/pic_trans.png"));
byte[] buffer = new byte[1024];
int len;
while ((len = is.read(buffer)) != -1){
fos.write(buffer, 0, len);
}
System.out.println("收到文件，来自：" + sock.getInetAddress().getHostAddress());
} 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 (sock != null) {
try {
sock.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (ss != null) {
try {
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
完成发送以后服务端返回值
尤其注意IO是阻塞式的，如果不停止流那么流不会停止的，需要sock.shutdownOutput();来停止阻塞
@Test
public void client() {
Socket sock = null;
OutputStream os = null;
FileInputStream fis = null;
try {
InetAddress inet = InetAddress.getByName("192.168.1.103");
sock = new Socket(inet, 9090);
os = sock.getOutputStream();
fis = new FileInputStream(new File("IOTest/pic1.png"));
//传输文件
byte[] buffer = new byte[1024];
int len;
while ((len = fis.read(buffer)) != -1){
os.write(buffer, 0, len);
}
//给出指令，停止输出文件，防止read()发生阻塞
sock.shutdownOutput();
//获得服务器反馈
InputStream is = sock.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] bufferr = new byte[5];
int len1;
while ((len1 = is.read(bufferr)) != -1){
baos.write(bufferr, 0, len1);
}
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 (sock != null) {
try {
sock.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
@Test
//文件传输服务端
public void server() {
ServerSocket ss = null;
Socket sock = null;
InputStream is = null;
FileOutputStream fos = null;
try {
ss = new ServerSocket(9090);
sock = ss.accept();
is = sock.getInputStream();
fos = new FileOutputStream(new File("IOTest/pic_trans.png"));
//接收文件
byte[] buffer = new byte[1024];
int len;
while ((len = is.read(buffer)) != -1){
fos.write(buffer, 0, len);
}
System.out.println("收到文件，来自：" + sock.getInetAddress().getHostAddress());
//服务器端给予客户端一个反馈
OutputStream os = sock.getOutputStream();
os.write("文件接收成功".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 (sock != null) {
try {
sock.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (ss != null) {
try {
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
UDP网络编程
@Test
//发送端
public void sender() {
DatagramSocket socket = null;
try {
InetAddress inet = InetAddress.getByName("192.168.1.103");
socket = new DatagramSocket();
String str = "我是UDP方式发送的这条信息";
byte[] data = str.getBytes();
DatagramPacket packet = new DatagramPacket(data, 0, data.length, inet, 9090);
socket.send(packet);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null)
socket.close();
}
}
@Test
//接收端
public void receiver() {
DatagramSocket socket = null;
try {
socket = new DatagramSocket(9090);
byte[] buffer = new byte[1024];
DatagramPacket dp = new DatagramPacket(buffer, 0, buffer.length);
socket.receive(dp);
System.out.println(new String(dp.getData(), 0, dp.getData().length));
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null)
socket.close();
}
}
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