How to write code to implement communication client using Socket in Java

 
import java.net.*; 
 
import java.io.*; 
 
import org.apache.log4j.Logger; 
 
public class SocketClient { 
 
static Logger log = Logger.getLogger(SocketClient.class.
getName()); //日志记录信息 
 
private String hostName; 
 
private int portNum; 
 
private int delaySecond; // 发文接收返回报文延时 
 
public SocketClient() { 
 
this.hostName = "192.168.0.1"; 
 
this.portNum = 7000; 
 
this.delaySecond = 50000; 
 
pFileOp = null; 
 
} 
 
private Socket getSocket() { 
 
Socket socket = null; 
 
try { 
 
socket = new Socket(hostName, portNum); 
 
} catch (UnknownHostException e) { 
 
System.out.println("-->未知的主机名:" + hostName + " 异常"); 
 
} catch (IOException e) { 
 
System.out.println("-hostName=" + hostName + " portNum=" 
 
+ portNum + "---->IO异常错误" + e.getMessage()); 
 
} 
 
return socket; 
 
} 
 
public String sendMessage(String strMessage) { 
 
String str = ""; 
 
String serverString = ""; 
 
Socket socket; 
 
try { 
 
socket = getSocket(); 
 
// socket.setKeepAlive(true); 
 
if (socket == null) { // 未能得到指定的Socket对象,Socket通讯为空 
 
return "0001"; 
 
} 
 
PrintWriter out = new PrintWriter(socket.getOutputStream()); 
 
//log.info("---->发送报文="+strMessage); 
 
out.println(strMessage); 
 
out.flush(); 
 
BufferedReader in = new BufferedReader(new InputStreamReader( 
 
socket.getInputStream())); 
 
long sendTime = System.currentTimeMillis(); 
 
long receiveTime = System.currentTimeMillis(); 
 
boolean received = false; // 成功接收报文 
 
boolean delayTooLong = false; 
 
serverString = null; 
 
while (!received && !delayTooLong) { 
 
if (socket.getInputStream().available() > 0) { 
 
// serverString = in.readLine(); 
 
char tagChar[]; 
 
tagChar = new char[1024]; 
 
int len; 
 
String temp; 
 
String rev = ""; 
 
if ((len = in.read(tagChar)) != -1) { 
 
temp = new String(tagChar, 0, len); 
 
rev += temp; 
 
temp = null; 
 
} 
 
serverString = rev; 
 
} 
 
receiveTime = System.currentTimeMillis(); 
 
if (serverString != null) 
 
received = true; // 字符串不为空，接收成功 
 
if ((receiveTime - sendTime) > delaySecond) 
 
delayTooLong = true; // 接收等待时间过长，超时 
 
} 
 
in.close(); 
 
out.close(); 
 
str=serverString; 
 
if (delayTooLong) str="2190"; //超时标志为真，返回超时码 
 
if (!received) str ="2190"; 
 
socket.close(); 
 
} catch (UnknownHostException e) { 
 
log.error("---->出现未知主机错误! 主机信息=" + this.hostName + 
" 端口号=" 
 
+ this.portNum + " 出错信息=" + e.getMessage()); 
 
str = "2191"; 
 
// System.exit(1); 
 
} catch (IOException e) { 
 
log.error("---->出现IO异常! 主机信息=" + this.hostName + 
" 端口号=" 
 
+ this.portNum + " 出错信息=" + e.getMessage()); 
 
e.printStackTrace(); 
 
str = "2191"; 
 
} catch (Exception e) { 
 
str="2177"; 
 
log.error("---->出现未知异常" + e.getMessage()); 
 
} finally { 
 
socket = null; 
 
str.trim(); 
 
//log.info("--->返回的socket通讯字符串="+str); 
 
return str; 
 
} 
 
} 
 
}