java.net.SocketTimeoutException: connect timed out 
客户端异常:connect timed out 
  at java.net.PlainSocketImpl.socketConnect(Native Method) 
  at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345) 
  at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) 
  at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) 
  at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) 
  at java.net.Socket.connect(Socket.java:589) 

while (1) { 
        jlong newTime; 
#ifndef USE_SELECT 
        { 
          struct pollfd pfd; 
          pfd.fd = fd; 
          pfd.events = POLLOUT; 
 
          errno = 0; 
          connect_rv = NET_Poll(&pfd, 1, timeout); 
        } 
#else 
        { 
          fd_set wr, ex; 
          struct timeval t; 
 
          t.tv_sec = timeout / 1000; 
          t.tv_usec = (timeout % 1000) * 1000; 
 
          FD_ZERO(&wr); 
          FD_SET(fd, &wr); 
          FD_ZERO(&ex); 
          FD_SET(fd, &ex); 
 
          errno = 0; 
          connect_rv = NET_Select(fd+1, 0, &wr, &ex, &t); 
        } 
#endif 
 
        if (connect_rv >= 0) { 
          break; 
        } 
        if (errno != EINTR) { 
          break; 
        } 
 
        /* 
         * The poll was interrupted so adjust timeout and 
         * restart 
         */ 
        newTime = JVM_CurrentTimeMillis(env, 0); 
        timeout -= (newTime - prevTime); 
        if (timeout <= 0) { 
          connect_rv = 0; 
          break; 
        } 
        prevTime = newTime; 
 
      } /* while */ 
 
      if (connect_rv == 0) { 
        JNU_ThrowByName(env, JNU_JAVANETPKG "SocketTimeoutException", 
              "connect timed out"); 
 
        /* 
         * Timeout out but connection may still be established. 
         * At the high level it should be closed immediately but 
         * just in case we make the socket blocking again and 
         * shutdown input & output. 
         */ 
        SET_BLOCKING(fd); 
        JVM_SocketShutdown(fd, 2); 
        return; 
      } 

newTime = JVM_CurrentTimeMillis(env, 0); 
        timeout -= (newTime - prevTime); 
        if (timeout <= 0) { 
          connect_rv = 0; 
          break; 
        } 

cat /proc/sys/net/ipv4/tcp_max_syn_backlog 

ss -lt 

<Connector executor="tomcatThreadPool" 
      port="8080"  
        protocol="HTTP/1.1" 
          acceptCount="5000" 
          connectionTimeout="25000" 
          maxHttpHeaderSize="8192" 
          useBodyEncodingForURI="true" 
          enableLookups="false"  
          redirectPort="8443"  
          URIEncoding="UTF-8"  
          maxThreads="500" 
          maxKeepAliveRequests="1000" 
          keepAliveTimeout="30000" 
        /> 

cat /proc/sys/net/core/somaxconn 

net.core.somaxconn = 8192 

<strong>countUpOrAwaitConnection</strong>(); 
 
         Socket socket = null; 
         try { 
           // Accept the next incoming connection from the server 
           // socket 
           socket = serverSocketFactory.acceptSocket(serverSocket); 
         } catch (IOException ioe) { 
           countDownConnection(); 
           // Introduce delay if necessary 
           errorDelay = handleExceptionWithDelay(errorDelay); 
           // re-throw 
           throw ioe; 
         }