[英]How to keep TCP sockets open?
Our application has a ping-pong like conversation with many servers (each server has a corresponding thread where those connections are made). 我们的应用程序具有与许多服务器的类似乒乓的对话(每个服务器都有一个用于建立这些连接的对应线程)。 Code below works, but it opens a new connection for every new request and is used only once, which soon leads to reaching max connection cap set by server.
下面的代码可以工作,但是它为每个新请求打开一个新连接,并且只能使用一次,这很快就会达到服务器设置的最大连接上限。
DataProvider.java DataProvider.java
public static ZnResult sendTcpQuery(String xml, String url, int port) {
List<ZnXmlResult> results = new ArrayList<>();
String xmlString = xml != null ? new String((xml + "\n").getBytes()) : "";
int error = ZnResult.OK;
try (Socket clientSocket = new Socket(url, port)) {
clientSocket.setSoTimeout(CONNECTION_TIMEOUT);
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
try (BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream(), "UTF-8"))) {
outToServer.writeBytes(xmlString);
try (StringWriter responseFromServer = new StringWriter()) {
String readLine;
while ((readLine = inFromServer.readLine()) != null) {
...
}
}
outToServer.close();
clientSocket.close();
}
} catch (Exception ex) {
LOG.error("Exception {}", url + ":" + port, ex);
error = ZnResult.ERR;
}
return error == ZnResult.OK ? new ZnResult(results) : new ZnResult(error);
}
How can I transform it, so everything can be done within one connection? 如何转换它,以便所有事情都可以在一个连接中完成? I figured I would do something like this:
我想我会做这样的事情:
SocketFactory.java SocketFactory.java
public class SocketFactory {
private static HashMap<String, Socket> socketsByAddress = new HashMap<>();
private static HashMap<Socket, DataOutputStream> outputStreamsBySocket = new HashMap<>();
private static HashMap<Socket, BufferedReader> readersBySocket = new HashMap<>();
public static Socket getSocket(String address) {
String ip = Tools.getIpFromAddress(address);
int port = Tools.getPortFromAddress(address);
Socket socket = socketsByAddress.get(address);
if (socket == null) {
try {
socket = new Socket(ip, port);
socket.setSoTimeout(60000);
socketsByAddress.put(address, socket);
} catch (IOException ex) {
Logger.getLogger(SocketFactory.class.getName()).log(Level.SEVERE, null, ex);
}
}
return socket;
}
public static DataOutputStream getOutputStream(Socket socket) {
DataOutputStream outputStream = outputStreamsBySocket.get(socket);
if (outputStream == null) {
try {
outputStream = new DataOutputStream(socket.getOutputStream());
outputStreamsBySocket.put(socket, outputStream);
} catch (IOException ex) {
Logger.getLogger(SocketFactory.class.getName()).log(Level.SEVERE, null, ex);
}
}
return outputStream;
}
public static BufferedReader getReader(Socket socket) {
BufferedReader reader = readersBySocket.get(socket);
if (reader == null) {
try {
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
readersBySocket.put(socket, reader);
} catch (IOException ex) {
Logger.getLogger(SocketFactory.class.getName()).log(Level.SEVERE, null, ex);
}
}
return reader;
}
}
DataProvider.java DataProvider.java
public static ZnResult sendTcpQuery(String xml, String url, int port) {
List<ZnXmlResult> results = new ArrayList<>();
int error = ZnResult.OK;
try {
String xmlString = xml != null ? new String((xml + "\n").getBytes()) : "";
Socket clientSocket = SocketFactory.getSocket(url + ":" + port);
DataOutputStream outToServer = SocketFactory.getOutputStream(clientSocket);
BufferedReader inFromServer = SocketFactory.getReader(clientSocket);
outToServer.writeBytes(xmlString);
try (StringWriter responseFromServer = new StringWriter()) {
String readLine;
while ((readLine = inFromServer.readLine()) != null) {
...
}
}
} catch (Exception ex) {
LOG.error("Exception {}", url + ":" + port, ex);
error = ZnResult.ERR;
}
return error == ZnResult.OK ? new ZnResult(results) : new ZnResult(error);
}
but it just doesn't work and only the first one go through. 但是它只是行不通,只有第一个通过。
This loop reads until the end of the stream. 该循环读取直到流结束。
while ((readLine = inFromServer.readLine()) != null) {
A stream only ends once. 流仅结束一次。 ie you can't end the stream but later use it again.
即您不能结束流,但是稍后再使用它。
What you need to do instead; 您需要做什么?
"[EOF]"
"[EOF]"
尝试像第一个代码中那样使用URL而不是IP地址来初始化Socket对象,然后查看它是否对您有用。
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