安卓套接字异常 "socket is closed"

Question

当我尝试使用以下代码运行由 echo 服务器和 android 客户端组成的测试时，我总是收到异常消息“套接字已关闭”。这段代码可以简单地向服务器发送消息，并从服务器接收消息，但是如果你想同时做这两件事，那是行不通的……我很好奇为什么会导致这种问题，如果我希望它能够首先将消息发送到回显服务器，我应该如何修复它

然后从回显服务器接收消息？

            // Server IP address 
            InetAddress serverIp;

            // try to connect Server
            try {

                // set up server IP address
                serverIp = InetAddress.getByName("192.168.17.1");

                // set up port
                int serverPort=12345;

                // initiate socket connection
                Socket clientSocket=new Socket(serverIp,serverPort);

                BufferedOutputStream out = new BufferedOutputStream(clientSocket.getOutputStream());
                out.write("Send From Android1111, stitch ".getBytes());
                out.flush();

                //wait to receive Server's msg 
                BufferedReader  br =new BufferedReader(new InputStreamReader(clientSocket.getInputStream())); 

                total.toString();*/
            // Display received msg with Toast
                Toast.makeText(getApplicationContext(), br.readLine(), Toast.LENGTH_SHORT ).show();

            //close connection
                clientSocket.close();             

//              out.close();
//              out = null;
            } catch (IOException e) {
                // display exception with Toast
                Toast.makeText(getApplicationContext(),e.toString(), Toast.LENGTH_SHORT).show();
            }

---

不幸的是，它仍然不起作用......我按照你的指示修改了代码:

            // set up Server IP address 
            serverIp = InetAddress.getByName("192.168.2.2");

            // set up Server port
            int serverPort=12345;

            // initiate socket connection
            Socket clientSocket=new Socket(serverIp,serverPort);

                // open input and output stream
            OutputStream out = clientSocket.getOutputStream();
            InputStream in = clientSocket.getInputStream();

            //send msg
            out.write("Send From Android1111, bitch ".getBytes());


                // receive msg from server
            byte[] buffer = new byte[in.available()];
            in.read(buffer);
            String rMsg = new String(buffer);
            Toast.makeText(getApplicationContext(), rMsg, Toast.LENGTH_LONG ).show();

            //close input and output stream
            in.close();
            out.close();

             //關閉連線
       clientSocket.close(); 
        } catch (IOException e) {
            // 出錯後顯示錯誤訊息Toast
            Toast.makeText(getApplicationContext(),e.toString(), Toast.LENGTH_SHORT).show();
        }

为了帮助者的方便，这里是服务器部分的 python 编写的代码:

# Practice Echo Server Program written in Python
import socket

# host = '' means it binds to any available interface
host = ''
port = 12345

# socket() function returns a socket object whose methods implement the various socket system calls.
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)

# Bind the socket to address. 
s.bind((host,port))

# Listen for connections made to the socket. The backlog argument specifies 
# the maximum number of queued connections and should be at least 0; 
# the maximum value is system-dependent (usually 5), the minimum value is forced to 0.
s.listen(5)

# Accept a connection. The socket must be bound to an address and listening for 
# connections. The return value is a pair (conn, address) where conn is a new socket 
# object usable to send and receive data on the connection, and address is the address
# bound to the socket on the other end of the connection.
conn, addr = s.accept()
print 'Connected by', addr

# Receive data from the socket. The return value is a string representing the data received.
# The maximum amount of data to be received at once is specified by bufsize. See the Unix
# manual page recv(2) for the meaning of the optional argument flags; it defaults to zero.
# Note For best match with hardware and network realities, the value of bufsize should be 
# a relatively small power of 2, for example, 4096.

while 1:
    data = conn.recv(1024)
    if not data: break 
    print 'received data is : ', repr(data)
    conn.send(data)

conn.close()

Answer 1

我假设您以错误的顺序做正确的事情。可能是服务器速度太快，当您尝试读取响应时，它已经收到并消失了。

遵循教程中提供的规则 Reading from and Writing to a Socket

1. 打开一个套接字
2. 打开输入流和输出流到套接字。
3. 根据服务器的协议(protocol)读取和写入流。
4. 关闭流。
5. 关闭 socket 。

你看出区别了吗？首先打开输入和输出流，然后开始发送您的请求。

我相信，如果您坚持这个顺序，它就会奏效。