TCP(Transmission Control Protocol 传输控制协议)是一种面向连接的、可靠的、基于字节流的传输层通信协议.
面向连接：服务器创建一个连接端口，客户端去连接服务器实现通信。
可靠的：tcp协议是是在连接成功之后才会发送数据，而基于UDP的协议是事先不会征求对方意见，直接将数据传送出去，因此TCP协议传输中，数据更可靠，更安全。
基于字节流：tcp协议中传递的信息是以流的形式传递的，在java中可通过inputstream来捕获，通过outputstream发送。
对于接收数据的时候出现假死的状态：
readLine()函数读取一行，结尾需要”\n”才能结束，不然会一直卡死在这里，因此大家在用printwriter的时候要print一个”\n”，然后把printwriter flush掉。就不会假死了！
这样：pw.write(“fuck you cient”); //send to server
pw.write(“\n”);
pw.flush();
在java中，tcp协议是已经封装好的类，可直接供用户使用。其中关键的两个类是
Socket类 ServerSocket类。
ServerSocket类用来创建服务器，具体用法请参照jdk文档。常用用法是
ServerSocket ss = new ServerSocket((int)port) //传入一个端口号，用户自定
Socket用于控制两端的连接，服务器的Socket可以和客户端的Socket相连接：
socket可以使用inputstream和outputstream进行相互通信。
(服务器中通常是将已将建立连接的socket丢给子线程通信，但是点对点可以让服务器处理一个socket就行了，不需要再生成子线程进行通信交流)
代码分为三个文件。
程序运行结果：
以下是代码附上：
//package org.cat.Client;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
public class MyClient {
public static void main(String[] args){
try {
Socket s = new Socket(“localhost”, 12341);
System.out.println(“conneting to server successfully”);
//successfully connecting to server
//Now sending some data to server
//1.create outputStream and so on…
OutputStream out = s.getOutputStream();
PrintWriter pw = new PrintWriter(out);
pw.write(“fuck you server”);//send to server
pw.write(“\n”);//important
pw.flush();
System.out.println(“I have sended to server”);
//2.receiving data from server
InputStream in = s.getInputStream();
InputStreamReader inReader = new InputStreamReader(in);
BufferedReader bfdReader = new BufferedReader(inReader);
String tmp = “xxxx,receiving failed”;
while((tmp = bfdReader.readLine()) != null)
System.out.println(“server tells:”+tmp);
//close all
in.close();inReader.close();bfdReader.close();
out.close();pw.close();
} catch (IOException e) {
System.out.println(“connecting failed,have u opened server?”);
e.printStackTrace();
}
}
}
//package org.cat.Server;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class MyServer {
public static void main(String[] args){
try {
@SuppressWarnings(“resource”)
ServerSocket sers = new ServerSocket(12341);
//then wait for client to connect
Socket s;
System.out.println(“waiting for client to connect”);
s = sers.accept();
new MyThread(s);
} catch (IOException e) {
System.out.println(“set up server failed??”);
e.printStackTrace();
}
}
}
//package org.cat.Server;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
public //service for every client
class MyThread extends Thread{
Socket s;
public MyThread(Socket s) {
this.s = s;
start();
//telling that connection has been settle up
System.out.println(“successed to connet with port of”+s.getLocalPort());
//now receiving data and talk back to client
//1.receive
try {
InputStream in = s.getInputStream();
InputStreamReader inReader = new InputStreamReader(in);
BufferedReader bfdReader = new BufferedReader(inReader);
String tmp = “xxxx,receiving failed”;
if((tmp = bfdReader.readLine()) != null)
System.out.println(“client tells:”+tmp);
//anwser client
OutputStream out = s.getOutputStream();
PrintWriter pw = new PrintWriter(out);
pw.write(“fuck you cient”);//send to server
pw.write(“\n”);
pw.flush();
System.out.println(“I have sended to client”);
//close all
out.close();pw.close();
in.close();inReader.close();bfdReader.close();
} catch (IOException e1) {
System.out.println(“get inputStream from client failed”);
e1.printStackTrace();
}
System.out.println(“now to shut connection”);
try {
s.close();
System.out.println(“shut down connection successfully”);
} catch (IOException e) {
System.out.println(“shut server failed,have u opened it?”);
e.printStackTrace();
}
}
}