一、TCP/UDP對比

二、TCP編程

TCP字節(jié)流編程
- Server端：

public class TCPServerStream {public static void main(String[] args) {/** 1.在本機的 9999 端口監(jiān)聽，等待連接* 2.當(dāng)沒有客戶端鏈接9999端口時，程序會阻塞，等待鏈接* 3.通過socket.getInputStream()讀取客戶端寫入到數(shù)據(jù)通道的數(shù)據(jù)，顯示*///注意細(xì)節(jié)：則個ServerSocket可以通過accept()返回多個Socket[多個客戶端鏈接服務(wù)器的并發(fā)]try (ServerSocket serverSocket = new ServerSocket(9999)) {System.out.println("server start at port:9999....");//有鏈接時返回socket對象Socket accept = serverSocket.accept();System.out.println("client has already connected");try (InputStream inputStream = accept.getInputStream();OutputStream outputStream = accept.getOutputStream()) {byte[] bytes=new byte[1024];int text;while ((text=inputStream.read(bytes))!=-1){System.out.println(new String(bytes,0,text));}//發(fā)送給client端信息outputStream.write("hello client".getBytes());System.out.println("server exit...");}} catch (IOException e) {e.printStackTrace();};} }

• client端

public class TCPClientStream {public static void main(String[] args) {/** 1.鏈接服務(wù)端(ip+port)* 2.連接上后，生成Socket，通過socket.getOutputStream()* 3.將數(shù)據(jù)寫入到數(shù)據(jù)通道*///鏈接本機：9999 端口System.out.println("client connecting......");try (Socket socket = new Socket(InetAddress.getLocalHost(), 9999)) {System.out.println("client connected......");//得到與socket相關(guān)聯(lián)的輸出流對象，發(fā)送信息try (OutputStream outputStream = socket.getOutputStream();InputStream inputStream=socket.getInputStream()) {//發(fā)送完一個消息后，要有結(jié)束標(biāo)記（socket.shutdownOutput();），不然會阻塞outputStream.write(("hello server".getBytes()));//非buffer字節(jié)流，無需flush//outputStream.flush();//單方向關(guān)閉client端的輸出流(不會關(guān)閉socket)，不然會阻塞socket.shutdownOutput();byte[] bytes=new byte[1024];int text;while ((text=inputStream.read(bytes))!=-1){System.out.println(new String(bytes,0,text));}System.out.println("client exit...");}} catch (IOException e) {e.printStackTrace();}} }

注意：

• 這里調(diào)用Socket的shutdownOutput()方法，底層會告知服務(wù)端我這邊已經(jīng)寫完了，那么服務(wù)端收到消息后，就能知道已經(jīng)讀取完消息，如果服務(wù)端有要返回給客戶的消息那么就可以通過服務(wù)端的輸出流發(fā)送給客戶端，如果沒有，直接關(guān)閉Socket。
• 這種方式通過關(guān)閉客戶端的輸出流，告知服務(wù)端已經(jīng)寫完了，雖然可以讀到服務(wù)端發(fā)送的消息，但是還是有一點缺點：不能再次發(fā)送消息給服務(wù)端，如果再次發(fā)送，需要重新建立Socket連接這個缺點，在訪問頻率比較高的情況下將是一個需要優(yōu)化的地方。

優(yōu)化文章

TCP字符流編程

• server

public class TCPServerCharacterStream extends Thread{private ServerSocket serverSocket;public static void main(String[] args) {TCPServerCharacterStream tcpServerCharacterStream=new TCPServerCharacterStream();tcpServerCharacterStream.start();}public TCPServerCharacterStream(){try{serverSocket = new ServerSocket(8888);}catch (Exception e){e.printStackTrace();}}@Overridepublic void run() {while (true){try {System.out.println("server waiting for connecting....");//阻塞等待連接Socket accept = serverSocket.accept();System.out.println("client has already connected....");try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(accept.getInputStream(), "UTF-8"));BufferedWriter bufferedWriter=new BufferedWriter(new OutputStreamWriter(accept.getOutputStream(),"UTF-8"))) {System.out.println("using socket is: "+accept);System.out.println("get message : "+bufferedReader.readLine());//給客戶端發(fā)送bufferedWriter.write("hello client from server");//結(jié)束標(biāo)志bufferedWriter.newLine();System.out.println("server exit....");}} catch (IOException e) {e.printStackTrace();}}} }

• client

public class TCPClientCharacterStream extends Thread{public static void main(String[] args) {System.out.println("client connecting......");try (Socket socket = new Socket(InetAddress.getLocalHost(), 8888)) {System.out.println("client connected......");try (BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF-8"));BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream(),"UTF-8"))){System.out.println("start to send message....");//給服務(wù)端發(fā)送System.out.println("using socket is: "+socket);bufferedWriter.write("sending: hello server from client");System.out.println("ending send message...");//結(jié)束標(biāo)記，要求接收方使用readLine()讀取;bufferedWriter.newLine();//try resource模式下，如果只是進(jìn)行寫操作，不像我這樣讀寫切換的話，好像是會因為自動close而自動flush。//比如我server端里面，因為寫操作是在讀操作后面的，所以try resource自動close后也能正常運行。//但像我client里面，因為寫操作后，try resource段還沒運行完，就必須手動flush，才能提交。bufferedWriter.flush();System.out.println(socket.isClosed());System.out.println("get message : "+bufferedReader.readLine());System.out.println("client exit...");}} catch (IOException e) {e.printStackTrace();}} }

注意：

try resource模式下，如果只是進(jìn)行寫操作，不像我這樣讀寫切換的話，好像是會因為自動close而自動flush。比如我server端里面，因為寫操作是在讀操作后面的，所以try resource自動close后也能正常運行。但像我client里面，因為寫操作后，try resource段還沒運行完，就必須手動flush，才能提交。

總結(jié)

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