Question

我正在尝试让客户端连续发送空字符串。我无法在第四次尝试时启动客户端。请参阅“//问题在这里开始”。

我收到的控制台消息

Removed newline: 
consecutiveWarningCount: 0
Removed newline: 
consecutiveWarningCount: 1
Removed newline: 
consecutiveWarningCount: 2
Removed newline: 
consecutiveWarningCount: 3
Removed newline: 
consecutiveWarningCount: 4
Removed newline: 
consecutiveWarningCount: 5

守则

//Load the tcp library
var net = require('net');

//Keep track of connected clients
var clients = [];

// Vars
var ADDRESS = '127.0.0.1';
var PORT = 3001;
var consecutiveWarningCount = 0;

//Start TCP Server
var s = net.createServer(function(cl) { 
  //console.log('Server connected');
  cl.setEncoding('utf8');
  cl.name = cl.remoteAddress + ":" + cl.remotePort;

  //Put the client into the list
  clients.push(cl);
  console.log('Pushed ' + cl.name + ' into client array');

  cl.on('end', function() {
    clients.splice(clients.indexOf(cl), 1);
    console.log('Server disconnected');
  });

  cl.on('data', function(data) {
    data = removeCarriageReturns(data);      //PROBLEM STARTS HERE.
    if (data.length == 0) {
      cl.write("You sent an empty string\r\n");
      consecutiveWarningCount += 1;
      console.log('consecutiveWarningCount: ' + consecutiveWarningCount);
    } 
    else if ((data.length == 0) && (consecutiveWarningCount == 1)) {
      cl.write("You sent an empty string again. This is your first warning.");
      consecutiveWarningCount += 1;
      console.log('consecutiveWarningCount: ' + consecutiveWarningCount);
    } 
    else if ((data.length == 0) && (consecutiveWarningCount == 2)) {
      cl.write("You sent an empty string again. This is your second warning.");
      consecutiveWarningCount += 1;
      console.log('consecutiveWarningCount: ' + consecutiveWarningCount);
    } 
    else if ((data.length == 0) && (consecutiveWarningCount == 3)) {
      cl.write("You sent an empty string again. This is your last warning.");
      cl.write("You will be disconnected if you send one more empty string");
      consecutiveWarningCount += 1;
      console.log('consecutiveWarningCount: ' + consecutiveWarningCount);
    } 
    else if ((data.length == 0) && (consecutiveWarningCount == 4)) {
      cl.destroy();
      console.log('Kicked ' + cl.remoteAddress);
    }
    else {
      console.log('Server received "' + data + '" from ' + cl.remoteAddress + ':' + cl.remotePort);
      cl.write('Client wrote ' + data ); 
      if (consecutiveWarningCount > 0) {
        consecutiveWarningCount -= 1;
      }
    }
  }); 

}); //End server

s.listen(PORT, function() { //'listening' listener

  //Start up information about the server
  console.log('-----------------------------');
  console.log('Server bound to port: ' + PORT);
  console.log('-----------------------------');
  console.log('Server listening...');
});

// Custom functions
var removeCarriageReturns = function(str) {
  var regexp = /\r\n/g;
  var regexp_carriagereturn = /\r/g;
  var regexp_newline = /\n/g;

  if (str.charAt(str.length-1) == "\n") {
    str = str.substring(0, str.length-2);
    console.log("Removed newline: " + str);
    if (str.charAt(str.length-1) == "\r") {
      str = str.substring(0, str.length-2);
      console.log("Removed carriage return:" + str);
    }
  }
  return str;
}

Answer 1

看一下代码（假设data.length等于零）：

if (data.length == 0) {
   //fire always
} 
else if ((data.length == 0) && (consecutiveWarningCount == 1)) {
   //never fired because you write "else" which means data.length != 0 
}

尝试以这种方式重写代码：

if (data.length == 0) {
  if (consecutiveWarningCount == 0) {
    //You sent an empty string
  } else if (consecutiveWarningCount == 1) {
    //You sent an empty string again. This is your first warning
  } //... and so on
}

nodejs没有发挥作用

1 个答案: