问题描述
就像我将数据发送到服务器，并使用下面的代码（============行）将数据甚至是非常大的数据取回。这是我的实验，因为我需要一些中间解决方案，以便可以将Flutter应用程序连接到tcp套接字。为此，我选择auqeduct.io。今天，从加济（Gazi）的帮助下，我找到了可以在===========行之间完成我的代码的解决方案。
Likely I send data to server and get data back even very big data using code below between =========== lines. This was to my experiment for I need to some intermediate solution so I can connect my Flutter app to tcp socket. For this I choose auqeduct.io. Today help from Gazi I found the solution to complete my code between =========== lines.
因为我使用了auqeduct他们的handle函数
Because of I am using auqeduct their handle function look like this.
@override
Future<RequestOrResponse> handle(Request request) async {
因此，我尝试修改代码并使用Future返回套接字数据作为字符串。我可以使用下面的代码在===========行之间获取数据，但是我无法使用Future _handle（String _request）异步获取任何数据。
So, I try to modify my code and use Future to return socket data as string. I can get data using code below between =========== lines, but I cannot get any data using Future _handle(String _request) async.
_socket.listen（（data）打印数据无法将数据分配给字符串，因此我无法返回字符串。
_socket.listen((data) prints the data cannot assign data to string, so I cannot return string.
工作原理： print（ （1）$ _secureResponse）;
works: print("(1) $_secureResponse");
不起作用： _secureResponse = new String.fromCharCodes（data）.trim（）;
not worked: _secureResponse = new String.fromCharCodes(data).trim();
如果我不使用Future并将代码放入main（）内，则一切运行正常。
If I don't use Future and put the code inside main() all is working perfectly.
在测试服务器中，我发送 Hello World，并返回 Welcome Sir / Madam。
In my test server I send a "Hello World" and in return I get "Welcome Sir/Madam".
我的问题是：如何从Future中的Dart中返回套接字数据？
My question is: How to return socket data from Future in Dart?
import 'dart:async';
import 'dart:io';
import 'dart:convert';
Socket socket;
String _errorData;
String _secureResponse;
void main() async {
var _test = await _handle("Hello World");
print("Print _test: $_test");
}
Future<String> _handle(String _request) async {
print("Future Starts Here");
print("Request: $_request");
_errorData = "Server_Error";
if (_request != null) {
print("Request has data");
// =============================================================
Socket _socket;
await Socket.connect("192.168.22.120", 3000).then((Socket sock) {
_socket = sock;
_socket.listen((data) {
print("Socket start to listen to database");
// GET FROM SERVER *********************
_secureResponse = new String.fromCharCodes(data).trim();
print("(1) $_secureResponse");
}, onError: ((error, StackTrace trace) {
_secureResponse = _errorData;
print("(2) $_secureResponse");
}), onDone: ((){
_socket.destroy();
exit(0);
}), cancelOnError: false);
}).then((_) {
print("Socket sends data to database");
// SENT TO SERVER ************************
_socket.write('$_request\r\n');
}).catchError((AsyncError e) {
_secureResponse = _errorData;
print("(3) $_secureResponse");
exit(1);
});
// ==============================================================
} else {
_secureResponse = _errorData;
print("(4) $_secureResponse");
}
print("(6) $_secureResponse");
print("Future Ends Here");
return _secureResponse;
}
结果：
- 未来从这里开始
- 请求： Hello World
- 请求有数据套接字将数据发送到数据库
- （6）空。--预期返回 欢迎先生/女士
- 未来在这里结束
- Print_test：空 --- 预期返回 欢迎先生/女士
- 套接字开始监听数据库
- （1） 欢迎先生/女士
- Future Starts Here
- Request: "Hello World"
- Request has data Socket sends data to database
- (6) null. --- expected return "Welcome Sir/Madam"
- Future Ends Here
- Print_test: null --- expected return "Welcome Sir/Madam"
- Socket start to listen to database
- (1) "Welcome Sir/Madam"
推荐答案
这可能有用。我想您应该阅读有关流/期货/异步/等待的内容。
This might work. I think you should read up about streams/futures/async/await, though.
Future<String> _handle(String _request) async {
print("Future Starts Here");
print("Request: $_request");
_errorData = "Server_Error";
if (_request != null) {
print("Request has data");
// =============================================================
Socket _socket;
await Socket.connect("192.168.22.120", 3000).then((Socket sock) {
_socket = sock;
}).then((_) {
print("Socket sends data to database");
// SENT TO SERVER ************************
_socket.write('$_request\r\n');
return _socket.first;
}).then((data) {
print("Socket start to listen to database");
// GET FROM SERVER *********************
_secureResponse = new String.fromCharCodes(data).trim();
print("(1) $_secureResponse");
}).catchError((AsyncError e) {
_secureResponse = _errorData;
print("(3) $_secureResponse");
exit(1);
});
// ==============================================================
} else {
_secureResponse = _errorData;
print("(4) $_secureResponse");
}
print("(6) $_secureResponse");
print("Future Ends Here");
return _secureResponse;
}
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