# Server and client on a non-blocking socket # # explanation of socket handling: # https://docs.python.org/3/howto/sockets.html # https://realpython.com/python-sockets/ # https://stackoverflow.com/questions/5308080/python-socket-accept-nonblocking # import socket import select import sys # for argv import time # for time.sleep() import errno import os import subprocess class pyPlcTcpClientSocket(): def __init__(self, callbackAddToTrace): self.callbackAddToTrace = callbackAddToTrace self.sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) # https://stackoverflow.com/questions/29217502/socket-error-address-already-in-use # The SO_REUSEADDR flag tells the kernel to reuse a local socket in TIME_WAIT state, without # waiting for its natural timeout to expire. self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self.isConnected = False self.rxData = [] def addToTrace(self, s): self.callbackAddToTrace(s) def connect(self, host, port): try: self.addToTrace("TCP connecting to " + str(host) + " port " + str(port) + "...") # for connecting, we are still in blocking-mode because # otherwise we run into error "[Errno 10035] A non-blocking socket operation could not be completed immediately" # We set a shorter timeout, so we do not block too long if the connection is not established: #print("step1") self.sock.settimeout(0.5) #print("step2") # https://stackoverflow.com/questions/71022092/python3-socket-program-udp-ipv6-bind-function-with-link-local-ip-address-gi # While on Windows10 just connecting to a remote link-local-address works, under # Raspbian the socket.connect says "invalid argument". # host = "2003:d1:170f:d500:1744:89d:d921:b20f" # works # host = "2003:d1:170f:d500:2052:326e:cef9:ad07" # works # host = "fe80::c690:83f3:fbcb:980e" # invalid argument. Link local address needs an interface specified. # host = "fe80::c690:83f3:fbcb:980e%eth0" # ok with socket.getaddrinfo if (os.name != 'nt'): # We are at the Raspberry #print(host[0:5].lower()) if (host[0:5].lower()=="fe80:"): #print("This is a link local address. We need to add %eth0 at the end.") host = host + "%eth0" socket_addr = socket.getaddrinfo(host,port,socket.AF_INET6,socket.SOCK_DGRAM,socket.SOL_UDP)[0][4] #print(socket_addr) #print("step2b") # https://stackoverflow.com/questions/5358021/establishing-an-ipv6-connection-using-sockets-in-python # (address, port, flow info, scope id) 4-tuple for AF_INET6 # On Raspberry, the ScopeId is important. Just giving 0 leads to "invalid argument" in case # of link-local ip-address. #self.sock.connect((host, port, 0, 0)) self.sock.connect(socket_addr) #print("step3") self.sock.setblocking(0) # make this socket non-blocking, so that the recv function will immediately return self.isConnected = True except socket.error as e: self.addToTrace("TCP connection failed" + str(e)) self.isConnected = False def disconnect(self): # When connection is broken, the OS may still keep the information of socket usage in the background, # and this could raise the error "A connect request was made on an already connected socket" when # we try a simple connect again. # This is explained here: # https://www.codeproject.com/Questions/1187207/A-connect-request-was-made-on-an-already-connected try: self.sock.close() # Close is not just closing. It means destroying the socket object. So we # need a new one: self.sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) # https://stackoverflow.com/questions/29217502/socket-error-address-already-in-use # The SO_REUSEADDR flag tells the kernel to reuse a local socket in TIME_WAIT state, without # waiting for its natural timeout to expire. self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) pass except socket.error as e: # if it was already closed, it is also fine. pass self.isConnected = False def transmit(self, msg): if (self.isConnected == False): # if not connected, just ignore the transmission request return -1 totalsent = 0 MSGLEN = len(msg) while (totalsent < MSGLEN) and (self.isConnected): try: sent = self.sock.send(msg[totalsent:]) if sent == 0: self.isConnected = False self.addToTrace("TCP socket connection broken") return -1 totalsent = totalsent + sent except: self.isConnected = False return -1 return 0 # success def isRxDataAvailable(self): # check for availability of data, and get the data from the socket into local buffer. if (self.isConnected == False): return False blDataAvail=False try: msg = self.sock.recv(4096) except socket.error as e: err = e.args[0] if err == errno.EAGAIN or err == errno.EWOULDBLOCK: # this is the normal case, if no data is available # print('No data available') pass else: # a "real" error occurred # print("real error") # print(e) self.isConnected = False else: if len(msg) == 0: # print('orderly shutdown on server end') self.isConnected = False else: # we received data. Store it. self.rxData = msg blDataAvail=True return blDataAvail def getRxData(self): # provides the received data, and clears the receive buffer d = self.rxData self.rxData = [] return d class pyPlcTcpServerSocket(): def __init__(self, callbackAddToTrace): self.callbackAddToTrace = callbackAddToTrace # Todo: find the link-local IPv6 address automatically. #self.ipAdress = 'fe80::e0ad:99ac:52eb:85d3' #self.ipAdress = 'fe80::c690:83f3:fbcb:980e%15' self.ipAdress = '' self.tcpPort = 15118 # The port for CCS self.BUFFER_SIZE = 1024 # Normally 1024 # Concept explanation: # We create a socket, that is just listening for incoming connections. # Later in the cyclic loop, we use the "select" to wait for activity on this socket. # In case there is a connection request, we create a NEW socket, which will handle the # data exchange. The original socket is still listening for further incoming connections. # This would allow to handle multiple connections. self.ourSocket = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, 0) self.ourSocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self.ourSocket.bind((self.ipAdress, self.tcpPort)) self.ourSocket.listen(1) self.addToTrace("pyPlcTcpSocket listening on port " + str(self.tcpPort)) hostname=socket.gethostname() IPAddr=socket.gethostbyname(hostname) addressInfo = socket.getaddrinfo(hostname, None, socket.AF_INET6) #print("Your Computer Name is:"+hostname) self.addToTrace("The socket is linked the following IP addresses:") for i in range(0, len(addressInfo)): #fe80::4c46:fea5:b6c9:25a9 IPv6Addr = addressInfo[i][4][0] self.addToTrace(IPv6Addr) self.read_list = [self.ourSocket] self.rxData = [] def addToTrace(self, s): self.callbackAddToTrace(s) def isRxDataAvailable(self): return (len(self.rxData)>0) def getRxData(self): # provides the received data, and clears the receive buffer d = self.rxData self.rxData = [] return d def transmit(self, txMessage): numberOfSockets = len(self.read_list) if (numberOfSockets<2): # print("we have " + str(numberOfSockets) + ", we should have 2, one for accepting and one for data transfer. Will not transmit.") return -1 # Simplification: We will send to the FIRST open connection, even we would have more connections open. This is # ok, because in our use case we have exactly one client. totalsent = 0 MSGLEN = len(txMessage) while totalsent < MSGLEN: sent = self.read_list[1].send(txMessage[totalsent:]) if sent == 0: self.addToTrace("socket connection broken") return -1 totalsent = totalsent + sent return 0 # success def mainfunction(self): # The select() function will block until one of the socket states has changed. # We specify a timeout, to be able to run it in the main loop. timeout_s = 0.05 # 50ms readable, writable, errored = select.select(self.read_list, [], [], timeout_s) for s in readable: if s is self.ourSocket: # We received a connection request at ourSocket. # -> we create a new socket (named client_socket) for handling this connection. client_socket, address = self.ourSocket.accept() # and we append this new socket to the list of sockets, which in the next loop will be handled by the select. self.read_list.append(client_socket) self.addToTrace("Connection from " + str(address)) else: # It is not the "listener socket", it is an above created "client socket" for talking with a client. # Let's take the data from it: try: data = s.recv(1024) except: # The client closed the connection in the meanwhile. #print("The client closed the connection in the meanwhile.") data = None if data: # print("received data:", data) self.rxData = data else: self.addToTrace("connection closed") s.close() self.read_list.remove(s) def testServerSocket(): print("Testing the pyPlcTcpServerSocket...") s = pyPlcTcpServerSocket() print("Press Ctrl-Break for aborting") nLoops = 0 while True: s.mainfunction() nLoops+=1 if ((nLoops % 10)==0): print(str(nLoops) + " loops") if (s.isRxDataAvailable()): d = s.getRxData() print("received " + str(d)) msg = "ok, you sent " + str(d) print("responding " + msg) s.transmit(bytes(msg, "utf-8")) if ((nLoops % 50)==0): print("trying to send something else") msg = "ok, something else..." s.transmit(bytes(msg, "utf-8")) def testClientSocket(): print("Testing the pyPlcTcpClientSocket...") c = pyPlcTcpClientSocket() #c.connect('fe80::e0ad:99ac:52eb:85d3', 15118) #c.connect('fe80::e0ad:99ac:52eb:9999', 15118) #c.connect('localhost', 15118) c.connect('fe80::c690:83f3:fbcb:980e', 15118) print("connected="+str(c.isConnected)) if (c.isConnected): print("sending something to the server") c.transmit(bytes("Test", "utf-8")) for i in range(0, 10): print("waiting 1s") time.sleep(1) if (c.isRxDataAvailable()): d = c.getRxData() print("received " + str(d)) if ((i % 3)==0): print("sending something to the server") c.transmit(bytes("Test", "utf-8")) print("end") def testExtra(): print("testExtra") #findLinkLocalIpv6Address() if __name__ == "__main__": print("Testing pyPlcTcpSocket.py....") if (len(sys.argv) == 1): print("Use command line argument c for clientSocket or s for serverSocket") exit() if (sys.argv[1] == "c"): testClientSocket() exit() if (sys.argv[1] == "s"): testServerSocket() exit() if (sys.argv[1] == "x"): testExtra() exit() print("Use command line argument c for clientSocket or s for serverSocket")