检查ClientSocket在Java中是否已断开连接

创建套接字时，请先设置超时：

private int timeout    = 10000;private int maxTimeout = 25000;clientSocket.setSoTimeout(timeout);

这样，如果读取超时，您将获得

java.net.SocketTimeoutException

volatile long lastReadTime;try {    bufferedReader.read();    lastReadTime = System.currentTimeMillis();} catch (SocketTimeoutException e) {    if (!isConnectionAlive()) {        logger.info("ConNECTION TERMINATED!");        clientSocket.close();         setUpSocket(); //sets up the server to reconnect to the client    } else {        sendHeartBeat(); //Send a heartbeat to the client    }}public boolean isConnectionAlive() {    return System.currentTimeMillis() - lastReadTime < maxTimeout;}

解决此问题的一种常见方法是将超时设置为某个数字（例如10秒），然后跟踪上一次成功从套接字读取的时间。如果您的超时时间已达到2.5倍，请放弃客户端并关闭套接字（以防万一，将FIN数据包发送到另一端）。

如果心跳信号 _不会_从远程系统获得任何响应，而只是在连接断开时最终最终更早地产生IOException的一种方式，那么您可以这样做（假设sendHeartBeat本身不会抛出IOException）：

try {    if (bufferedReader.read() == -1) {        logger.info("ConNECTION TERMINATED with EOF!");        resetConnection();    }} catch (SocketTimeoutException e) {    // This just means our read timed out ... the socket is still good    sendHeartBeat(); //Send a heartbeat to the client} catch (IOException e) {    logger.info("ConNECTION TERMINATED with Exception " + e.getMessage());    resetConnection();}....private void resetConnection() {    clientSocket.close();     setUpSocket(); //sets up the server to reconnect to the client}