什么是套接字Socket
Socket本身就是網(wǎng)絡(luò)上的兩個(gè)程序可以互相發(fā)送請(qǐng)求和接收請(qǐng)求，應(yīng)用程序可以利用套接字在網(wǎng)絡(luò)上進(jìn)行數(shù)據(jù)傳輸。
Socket本身作為應(yīng)用程序和網(wǎng)絡(luò)層TCP/UDP之間的一個(gè)抽象層，在TCP中主要采用流套接字，采用的方式就是點(diǎn)對(duì)點(diǎn)通過字節(jié)流傳輸；UDP主要采用數(shù)據(jù)報(bào)套接字。
面向連接的入門例子
功能：客戶端發(fā)送請(qǐng)求，服務(wù)器接收請(qǐng)求
服務(wù)端：
public class MyServer {
class HandleTask {
private Socket socket;
public HandleTask() {}
public HandleTask(Socket socket) {
this.socket = socket;
}
public void handle() {
StringBuilder sb = new StringBuilder("Hello: ");
InputStream is = null;
BufferedReader br = null;
try {
is = socket.getInputStream();
br = new BufferedReader(new InputStreamReader(is));
sb.append(br.readLine());
System.out.println(sb.toString());
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (null != br) {
br.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if (null != is) {
is.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
try {
Thread.sleep(15000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(sb.toString() + "-- 結(jié)束執(zhí)行 --");
}
}
public static void main(String[] args) throws IOException{
ServerSocket serverSocket = null;
Socket socket = null;
try {
serverSocket = new ServerSocket(9999);
while (true) {
socket = serverSocket.accept();
new MyServer().new HandleTask(socket).handle();
}
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
if (null != socket) {
socket.close();
}
if (null != serverSocket) {
serverSocket.close();
}
}
}
}
思路：
① 服務(wù)器端啟動(dòng)了ServerSocket，然后綁定了端口9999。
② 調(diào)用accept方法，阻塞等待客戶端連接。
③ 當(dāng)接收到客戶端的請(qǐng)求之后，通過字節(jié)流獲取客戶端發(fā)來的信息。
多個(gè)客戶端：
public class MyClient {
public static void main(String[] args) {
Socket socket = null;
BufferedWriter bw = null;
Scanner scanner = new Scanner(System.in);
try {
socket = new Socket("localhost", 9999);
bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
bw.write(scanner.nextLine());
bw.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
scanner.close();
try {
if (null != bw) {
bw.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if (null != socket) {
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public class MyClient2 {
public static void main(String[] args) {
Socket socket = null;
BufferedWriter bw = null;
Scanner scanner = new Scanner(System.in);
try {
socket = new Socket("localhost", 9999);
bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
bw.write(scanner.nextLine());
bw.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
scanner.close();
try {
if (null != bw) {
bw.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if (null != socket) {
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
結(jié)果：
1.jpg
解釋：
上面這個(gè)例子的缺陷就是如果是多個(gè)請(qǐng)求去等待服務(wù)器端去處理，那么服務(wù)器端會(huì)按照收到請(qǐng)求的順序執(zhí)行，這樣如果第一個(gè)請(qǐng)求執(zhí)行時(shí)間很長(zhǎng)，那么第二個(gè)請(qǐng)求就很長(zhǎng)時(shí)間等不到執(zhí)行。
多線程執(zhí)行多個(gè)客戶端
場(chǎng)景：
基于上面的例子，思考：服務(wù)器在很多情況下是需要接收來自很多個(gè)客戶端的請(qǐng)求的。
解決辦法：
根據(jù)多線程時(shí)間分片方式來解決問題：多個(gè)客戶端的請(qǐng)求，那么服務(wù)器采用每次接收到一個(gè)請(qǐng)求就創(chuàng)建一個(gè)線程來執(zhí)行。
采用多線程改進(jìn)的服務(wù)端：
public class MyThreadServer {
class HandleTask extends Thread{
private Socket socket;
public HandleTask() {}
public HandleTask(Socket socket) {
this.socket = socket;
}
@Override
public void run() {
StringBuilder sb = new StringBuilder("Hello: ");
InputStream is = null;
BufferedReader br = null;
try {
is = socket.getInputStream();
br = new BufferedReader(new InputStreamReader(is));
sb.append(br.readLine());
System.out.println(sb.toString());
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (null != br) {
br.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if (null != is) {
is.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
try {
Thread.sleep(15000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(sb.toString() + "-- 結(jié)束執(zhí)行 --");
}
}
public static void main(String[] args) {
ServerSocket serverSocket = null;
Socket socket = null;
try {
serverSocket = new ServerSocket(9999);
while (true) {
socket = serverSocket.accept();
new MyThreadServer().new HandleTask(socket).start();
}
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
try {
if (null != socket) {
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if (null != serverSocket) {
serverSocket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
2.jpg
3.jpg
方案使用的模型：
上面的程序?qū)ｉT使用一個(gè)接收者線程來專門負(fù)責(zé)監(jiān)聽客戶端的請(qǐng)求，接收到客戶端的請(qǐng)求，就為其創(chuàng)建一個(gè)新的線程去執(zhí)行業(yè)務(wù)處理，最后通過字節(jié)流進(jìn)行返回響應(yīng)。這種模型就是BIO（阻塞IO）。
方案的缺點(diǎn)：
這種工作的模型有一個(gè)問題，就是當(dāng)請(qǐng)求數(shù)很多時(shí)，就會(huì)創(chuàng)建和請(qǐng)求數(shù)一樣多匹配線程。最終當(dāng)并發(fā)量上來，那么系統(tǒng)的性能將會(huì)下降。
線程池執(zhí)行多個(gè)客戶端
場(chǎng)景：
基于上面的例子，使用多線程方式來處理請(qǐng)求，每個(gè)請(qǐng)求都創(chuàng)建一個(gè)匹配的線程，浪費(fèi)線程資源。采用線程池管理線程，可以充分利用線程。
采用線程池改進(jìn)的服務(wù)端：
public class MyThreadPoolServer {
private static ExecutorService es = Executors.newCachedThreadPool();
class HandleTask extends Thread {
private Socket socket;
public HandleTask() {}
public HandleTask(Socket socket) {
this.socket = socket;
}
@Override
public void run() {
StringBuilder sb = new StringBuilder("Hello: ");
InputStream is = null;
BufferedReader br = null;
try {
is = socket.getInputStream();
br = new BufferedReader(new InputStreamReader(is));
sb.append(br.readLine());
System.out.println(sb.toString());
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (null != br) {
br.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if (null != is) {
is.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
try {
Thread.sleep(15000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(sb.toString() + "-- 結(jié)束執(zhí)行 --");
}
}
public static void main(String[] args) {
ServerSocket serverSocket = null;
Socket socket = null;
try {
serverSocket = new ServerSocket(9999);
while (true) {
socket = serverSocket.accept();
es.execute(new MyThreadServer().new HandleTask(socket));
}
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
try {
if (null != socket) {
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if (null != serverSocket) {
serverSocket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
4.jpg
方案使用的模型：
5.jpg
