Python twisted ssh client: client blocks after sending 10 commands

Question

I started using twisted recently, and I'm trying to create a client that connects and sends commands to an SSH server. (I'm only creating the client and using some SSH server to test it). After sending 10 commands (e.g 'ls' command) and receiving an answer for each of the commands, my client is blocked. Can someone help me find a solution to this? Here is the most important part of my client. PS: I'm using twisted 12.0.0 (msi binaries).

class SimpleConnection(connection.SSHConnection):
    def serviceStarted(self):
        self.openChannel(CommandChannel(conn=self))

class CommandChannel(channel.SSHChannel):
    name = 'session'
    def channelOpen(self, data):
        global command
        command = "ls"
        d = self.conn.sendRequest(self, 'exec', common.NS(command), wantReply=True) 
        d.addCallback(self.dataReceived) 
    def dataReceived(self, data): 
        print (data)
    def closeReceived(self): 
        self.conn.openChannel(self)

Answer 1

The problem was that the server was blocking the session number 10: "[SSHChannel session (10) on SSHService ssh-connection on SimpleTransport,client] other side refused open reason: ('open failed', 1)". This is a normal behaviour, (MaxSessions in sshd_config which specifies the maximum number of open sessions permitted per network connection was set to 10).

SSHChannel always closes itself after running a command. So a new channel should be created for a new command, after the old channel was closed. Here is the most important part of my client corrected :

class SimpleConnection(connection.SSHConnection):
    def serviceStarted(self):
        self.openChannel(CommandChannel(conn=self)) 

class CommandChannel(channel.SSHChannel):
    name = 'session'
    def channelOpen(self, data): 
        global command
        command = "ls"
        d = self.conn.sendRequest(self, 'exec', common.NS(command), wantReply=True) 
        d.addCallback(self.dataReceived) 
    def dataReceived(self, data):  
        print (data)
    def closed(self):
        self.conn.serviceStarted()