Cannot connect to the server over TCP (116 error)

[LuckyMan]

Hi Nordic,

I am coding a program (TCP client) sending an array of bytes to a server over TCP. There is no error during the building process. And, there is also no error with modem initialization. But, I always receive the error 116 when I connect to the TCP server.

For the TCP server, I run a TCP server script in Python to receive the data from the TCP client, I tested the TCP server program by using the Netcat tool, and it works. So the problem comes from the code for nRF9160. 

I consulted a lot of credits on the Devzone, but I cannot find the problem. 

Could you please help me have a look at it? (I am using nRF SDK v2.5.1)

Best,

wu

Code_Nordic.zip

[Øyvind]

Hello, 

Difficult to tell. What server are you trying to connect? Could you please provide a modem trace and logs as well?

Here is what I get:

*** Booting nRF Connect SDK v2.5.1 ***
I: Starting bootloader
I: Primary image: magic=unset, swap_type=0x1, copy_done=0x3, image_ok=0x3
I: Secondary image: magic=unset, swap_type=0x1, copy_done=0x3, image_ok=0x3
I: Boot source: none
I: Image index: 0, Swap type: none
I: Bootloader chainload address offset: 0x10000
*** Booting nRF Connect SDK v2.5.1 ***
Connecting
Modem initialization...
LTE cell changed: Cell ID: 21627653, Tracking area: 33129
RRC mode: Connected
Network registration status: Connected - roaming

src PSM parameter update: TAU: 9000, Active time: -1
does not contain a character string representing a valid network address
Not able to initialize TCP server connection

IP address 2a05:d014:.............., Port number 7073

*********************************************
Data to send over LTE-M (as integers, with IMEI embedded as ASCII):
0       0       0       0       0       0       0       0       0       0       0       0       0       0       0       15      16      17      18      1920      21      22      23      1
*********************************************
Failed to transmit TCP packet, 9 Bad file number
RRC mode: Idle

Thanks.

Kind regards,
Øyvind

[LuckyMan]

Hi Øyvind,

 Thank you for your reply.

That is quite weird, I do not know the reason. I programmed the board to work as a UDP client to send data to a UDP server that is run on an AWS server, and it works well. But, when I tried to program it to work as a TCP client to send data to a TCP server run on AWS, the connection failed. The problem is that I do not where I am wrong.

- This is the log file: (for safety reason, I delete the IP address in the log fine )

*** Booting nRF Connect SDK v2.5.1 ***
Connecting
Modem initialization...
LTE cell changed: Cell ID: 103026701, Tracking area: 20100
RRC mode: Connected
Network registration status: Connected - home network
PSM parameter update: TAU: 3240, Active time: -1
RRC mode: Idle

RRC mode: Connected
Connect failed : 116
Closed the socket
Not able to initialize TCP server connection

IP address 2a05:d014:185:b700:b242....., Port number 7073

*********************************************
Data to send over LTE-M (as integers, with IMEI embedded as ASCII):
0       0       0       0       0       0       0       0       0       0       0       0       0       0  015      16      17      18      19      20      21      22      23      1
*********************************************
Failed to transmit TCP packet, 9 Bad file number
RRC mode: Idle

Everything is fine except error 116 (see line 11 in the Log file "Connect failed : 116"), when I try to connect to the TCP server.

- For the server: It is just a simple TCP server that is run on AWS to test. I tested the TCP server code by using the Netcat tool, there is no problem with the TCP server code.

import time                                                  
import socket
import struct                                              
from ctypes import *                                         
import sys                                                 
from datetime import datetime                               
                     
import signal                                               
import os                                                   
import json                                                 
import logging                                              




logging.basicConfig(                                        
    filename="TCP_RX_Log.log",                                
    filemode='a',                                           
    format='%(asctime)s %(levelname)-8s %(message)s',       
    level=logging.INFO,                                     
    datefmt='%Y-%m-%d %H:%M:%S')                            

# Declare IP address + Port
localIP = "2a05:d014:185:b700..........................."          # IPv6 of AWS where we run UDP code on
recvPort = 7073                                             
buffersize = 4096                                                                               
host = ''                                                   

# Create a TCP/IP socket  
try:
    r = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)      
    r.bind((host, recvPort))                                    
    print ("Binding successful!")
except:                                                         
    logging.critical("Failed to bind port")                     
    print("Failed to bind the port")
    sys.exit(1)


# In đường dẫn nơi chứa file Log (được tạo trên AWS)
logFile = os.getcwd() + "/TCP_RX_Log.log"                   
                                                            

#recvMsg, addr = r.recvfrom(buffersize)                     
def receiveMessage(connection, addr):                       
    # recvMsg, addr = r.recvfrom(buffersize)                
    recvMsg = connection.recv(buffersize)                    
    
    devIP = addr[0]                                                        
    devPort = addr[1]                                       
   
    try: 
        devIMEI = recvMsg[0:15].decode(encoding='UTF-8')    
    except:
        logging.error("Couldn't parse devIMEI")
        devIMEI = 0
    
    return devIP, devPort, devIMEI, recvMsg                


if __name__ == "__main__":
    logging.info("TCP server Started!")
    while 1:
        # Listen for incoming connections 
        r.listen()
        print ("waiting for a connection")
        connection, addr = r.accept()                            
        if connection:                                                            
            print (f"Connected to client: {addr}")
            devIP, devPort, devIMEI, recvMsg = receiveMessage(connection, addr)     
            if recvMsg:
                print ("Receive from client with IP: ", devIP, " and Port Number: ", devPort)
                print ("IMEI: ", devIMEI)

                for x in recvMsg:
                    print("- ", (x))

                # Close the connection 
                connection.close()

Thanks for your help!

Best,

wu