【转】java socket程序

【转】java socket程序
2009年09月21日
　　老久没有动手写Socket程序了，今天应同事的要求上了一段程序。
　　这是一段很简单与C++编写的服务端通讯的java客户端，咋一看上去，没有任何问题。
　　貌似没有问题的程序
　　Java代码 
　　
　　
　　public static String sendSynMsg(String ipAddr, byte[] datas) throws Exception{        //解析服务器地址和端口号        int dotPos = ipAddr.indexOf(':');        String ip = ipAddr.substring(0, dotPos).trim();        int port = Integer.parseInt(ipAddr.substring(dotPos+1).trim());        InetSocketAddress endpoint = new InetSocketAddress(ip , port);                Socket socket = null;        OutputStream out = null;        InputStream in = null;        try {                   socket = new Socket();            //设置发送逗留时间2秒            socket.setSoLinger(true, 2);             //设置InputStream上调用 read()阻塞超时时间2秒            socket.setSoTimeout(2000);            //设置socket发包缓冲为32k；            socket.setSendBufferSize(32*1024);            //设置socket底层接收缓冲为32k            socket.setReceiveBufferSize(32*1024);            //关闭Nagle算法.立即发包            socket.setTcpNoDelay(true);            //连接服务器            socket.connect(endpoint);            //获取输出输入流            out = socket.getOutputStream();            in = socket.getInputStream();            //输出请求                      out.write(datas);            out.flush();            //接收应答            BufferedReader br = new BufferedReader( new InputStreamReader(in) , 4096);            StringWriter received = new StringWriter(4096);            char[] charBuf = new char[4096];            int size = 0;            while ((size = br.read(charBuf)) > 0){                received.write(charBuf, 0, size);            }            return received.toString();                    } finally {            if (out != null) {                try {                    out.close();                } catch(Exception ex) {                    ex.printStackTrace();                }            }            if (in != null) {                try {                    in.close();                } catch(Exception ex) {                    ex.printStackTrace();                }            }                   if (socket != null) {                try {                    socket.close();                } catch(Exception ex) {                    ex.printStackTrace();                }            }        }                   } 
　　public static String sendSynMsg(String ipAddr, byte[] datas) throws Exception{ //解析服务器地址和端口号 int dotPos = ipAddr.indexOf(':'); String ip = ipAddr.substring(0, dotPos).trim(); int port = Integer.parseInt(ipAddr.substring(dotPos+1).trim()); InetSocketAddress endpoint = new InetSocketAddress(ip , port); Socket socket = null; OutputStream out = null; InputStream in = null; try { socket = new Socket(); //设置发送逗留时间2秒 socket.setSoLinger(true, 2); //设置InputStream上调用 read()阻塞超时时间2秒 socket.setSoTimeout(2000); //设置socket发包缓冲为32k； socket.setSendBufferSize(32*1024); //设置socket底层接收缓冲为32k socket.setReceiveBufferSize(32*1024); //关闭Nagle算法.立即发包 socket.setTcpNoDelay(true); //连接服务器 socket.connect(endpoint); //获取输出输入流 out = socket.getOutputStream(); in = socket.getInputStream(); //输出请求 out.write(datas); out.flush(); //接收应答 BufferedReader br = new BufferedReader( new InputStreamReader(in) , 4096); StringWriter received = new StringWriter(4096); char[] charBuf = new char[4096]; int size = 0; while ((size = br.read(charBuf)) > 0){ received.write(charBuf, 0, size); } return received.toString(); } finally { if (out != null) { try { out.close(); } catch(Exception ex) { ex.printStackTrace(); } } if (in != null) { try { in.close(); } catch(Exception ex) { ex.printStackTrace(); } } if (socket != null) { try { socket.close(); } catch(Exception ex) { ex.printStackTrace(); } } } }
　　但实际的调试中，总是报Read TimeOut异常！！排查原因后发现，数据是接收到了，只是size = br.read(charBuf)不会返回-1（java doc中的说明是读取到结束时size会返回-1）。
　　对于编写服务器端程序的C++程序员而言，他们通常会在通讯结束的时候，在数据的尾部加上一个\0的结束字符。因此，我们针对此做了修正
　　出问题的程序段
　　Java代码 
　　
　　
　　while ((size = br.read(charBuf)) > 0){        received.write(charBuf, 0, size);    } 
　　while ((size = br.read(charBuf)) > 0){ received.write(charBuf, 0, size); }
　　修改后的正确写法
　　Java代码 
　　
　　
　　char lastChar = 0;    do {        size = br.read(charBuf , 0 , 4096);        lastChar = charBuf[size-1];        if(lastChar == 0){            //去除尾部的\0字符            received.write(charBuf, 0, size - 1);        }    }while(lastChar != 0); 
　　char lastChar = 0; do { size = br.read(charBuf , 0 , 4096); lastChar = charBuf[size-1]; if(lastChar == 0){ //去除尾部的\0字符 received.write(charBuf, 0, size - 1); } }while(lastChar != 0);
　　最终的完整程序段：
　　Java代码 
　　
　　
　　private static String sendSynMsg(String ipAddr, byte[] datas) throws Exception{        //解析服务器地址和端口号        int dotPos = ipAddr.indexOf(':');        String ip = ipAddr.substring(0, dotPos).trim();        int port = Integer.parseInt(ipAddr.substring(dotPos+1).trim());        InetSocketAddress endpoint = new InetSocketAddress(ip , port);                Socket socket = null;        OutputStream out = null;        InputStream in = null;        try {                   socket = new Socket();            //设置发送逗留时间2秒            socket.setSoLinger(true, 2);             //设置InputStream上调用 read()阻塞超时时间2秒            socket.setSoTimeout(2000);            //设置socket发包缓冲为32k；            socket.setSendBufferSize(32*1024);            //设置socket底层接收缓冲为32k            socket.setReceiveBufferSize(32*1024);            //关闭Nagle算法.立即发包            socket.setTcpNoDelay(true);            //连接服务器            socket.connect(endpoint);            //获取输出输入流            out = socket.getOutputStream();            in = socket.getInputStream();            //输出请求                      out.write(datas);            out.flush();            //接收应答            BufferedReader br = new BufferedReader( new InputStreamReader(in) , 4096);            StringWriter received = new StringWriter(4096);            char[] charBuf = new char[4096];            int size = 0;            char lastChar = 0;            do {                size = br.read(charBuf , 0 , 4096);                lastChar = charBuf[size-1];                if(lastChar == 0){                    received.write(charBuf, 0, size - 1);                }                //System.out.println(received.toString());            }while(lastChar != 0);                        return received.toString();                    } finally {            if (out != null) {                try {                    out.close();                } catch(Exception ex) {                    ex.printStackTrace();                }            }            if (in != null) {                try {                    in.close();                } catch(Exception ex) {                    ex.printStackTrace();                }            }                   if (socket != null) {                try {                    socket.close();                } catch(Exception ex) {                    ex.printStackTrace();                }            }        }                   } 
　　private static String sendSynMsg(String ipAddr, byte[] datas) throws Exception{ //解析服务器地址和端口号 int dotPos = ipAddr.indexOf(':'); String ip = ipAddr.substring(0, dotPos).trim(); int port = Integer.parseInt(ipAddr.substring(dotPos+1).trim()); InetSocketAddress endpoint = new InetSocketAddress(ip , port); Socket socket = null; OutputStream out = null; InputStream in = null; try { socket = new Socket(); //设置发送逗留时间2秒 socket.setSoLinger(true, 2); //设置InputStream上调用 read()阻塞超时时间2秒 socket.setSoTimeout(2000); //设置socket发包缓冲为32k； socket.setSendBufferSize(32*1024); //设置socket底层接收缓冲为32k socket.setReceiveBufferSize(32*1024); //关闭Nagle算法.立即发包 socket.setTcpNoDelay(true); //连接服务器 socket.connect(endpoint); //获取输出输入流 out = socket.getOutputStream(); in = socket.getInputStream(); //输出请求 out.write(datas); out.flush(); //接收应答 BufferedReader br = new BufferedReader( new InputStreamReader(in) , 4096); StringWriter received = new StringWriter(4096); char[] charBuf = new char[4096]; int size = 0; char lastChar = 0; do { size = br.read(charBuf , 0 , 4096); lastChar = charBuf[size-1]; if(lastChar == 0){ received.write(charBuf, 0, size - 1); } //System.out.println(received.toString()); }while(lastChar != 0); return received.toString(); } finally { if (out != null) { try { out.close(); } catch(Exception ex) { ex.printStackTrace(); } } if (in != null) { try { in.close(); } catch(Exception ex) { ex.printStackTrace(); } } if (socket != null) { try { socket.close(); } catch(Exception ex) { ex.printStackTrace(); } } } }
　　程序中的关键点：
　　1. 不直接使用new Socket(String ip , int port)的构造函数，而是设置了socket的环境参数后再连接
　　2.设置发送逗留时间 socket.setSoLinger(true, 2); 这个参数是socket发送数据时的超时，如果对方在固定时间内不接受，则关闭socket。与socket.setSoTimeout(2000)不同，这个是设置InputStream上调用 read()阻塞超时时间。
　　3.socket.setTcpNoDelay(true);关闭Nagle算法。这使得在调用out.flush();时总能第一时间的发送数据包（这个适用于你的数据包是完整的一次性发送的前提）。
　　4.根据应用协议的实际大小，优化你的接收和发送缓冲，这两个参数可以有效提高网络通信的效率。
　　5.使用char的数组配合StringWriter作为接收数据的写入，这个比使用readLine方法实现更优雅。