3. TCP-Client Example Explanation

1. Environment Preparation

To ensure a smooth demonstration of TCP communication, we need to confirm that the following environment is correctly configured:

1.1 Hardware Connection

• Ensure that your CanMV development board and computer are connected to the same router or switch via an Ethernet cable to form a local area network.

• Ensure the router or switch is working properly to guarantee network connection stability.

1.2 Disable Firewall

• To avoid the firewall blocking TCP communication, it is recommended to temporarily disable the computer’s firewall.

1.3 Tool Preparation

• Download and install NetAssist Network Debugging Assistant as a network communication testing tool to help send and receive network data.

1.4 Obtain IP Address

• Open the Command Prompt (CMD), enter ipconfig, and query and record the IP address of the computer’s network card for subsequent configuration and testing.

2. Client Code Analysis

2.1 Import Necessary Libraries

import network  
import socket  
import time

• network: Used for network interface operations, such as configuring IP addresses and checking network status.

• socket: Provides the Socket interface for network communication.

• time: Provides functions related to time, such as delay (sleep).

2.2 Define Client Function

def client():  
    # ... (subsequent code)

• The client function contains the main logic of the TCP client.

2.3 Configure Network Interface

def network_use_wlan(is_wlan=True):
    if is_wlan:
        sta = network.WLAN(0)
        sta.connect("Canaan", "Canaan314")
        print(sta.status())
        while sta.ifconfig()[0] == '0.0.0.0':
            os.exitpoint()
        print(sta.ifconfig())
        ip = sta.ifconfig()[0]
        return ip
    else:
        a = network.LAN()
        if not a.active():
            raise RuntimeError("LAN interface is not active.")
        a.ifconfig("dhcp")
        print(a.ifconfig())
        ip = a.ifconfig()[0]
        return ip

Configure the network interface based on the parameters, as follows:

1. WLAN Mode:

   • If is_wlan=True, configure the wireless network interface (WLAN) and connect to the Wi-Fi with SSID “Canaan” and password “Canaan314”.

   • Wait and check if a valid IP address is assigned, then return the IP.

2. LAN Mode:

   • If is_wlan=False, configure the wired network interface (LAN), enable DHCP to automatically obtain an IP address, and return the IP.

2.4 Create Socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

• Create a Socket object using IPv4 (AF_INET) and TCP (SOCK_STREAM) protocol.

2.5 Obtain Server Address and Port

ai = socket.getaddrinfo("172.16.1.174", 8080)  
addr = ai[0][-1]  # Extract address and port

• Use getaddrinfo to obtain the server’s IP address and port number, and extract the address information.

2.6 Connect to Server

try:  
    s.connect(addr)  
    print("Connected to server:", addr)  
except Exception as e:  
    s.close()  
    print("Connection error:", e)  
    return

• Try to connect to the server. If the connection fails, print the error message and close the connection.

2.7 Send Data

for i in range(10):  
    message = "K230 TCP client send test {0} \r\n".format(i)  
    print("Sending:", message)  
    s.sendall(message.encode())  
    time.sleep(0.2)

• Send 10 test messages in a loop, using the sendall method to ensure each message is completely sent.

2.8 Close Socket

s.close()  
print("Client ends connection.")

• Close the Socket to release resources, indicating the client has ended the connection.

2.9 Complete Code Example

import network
import socket
import os, time

def network_use_wlan(is_wlan=True):
    if is_wlan:
        sta = network.WLAN(0)
        sta.connect("Canaan", "Canaan314")
        print(sta.status())
        while sta.ifconfig()[0] == '0.0.0.0':
            os.exitpoint()
        print(sta.ifconfig())
        ip = sta.ifconfig()[0]
        return ip
    else:
        a = network.LAN()
        if not a.active():
            raise RuntimeError("LAN interface is not active.")
        a.ifconfig("dhcp")
        print(a.ifconfig())
        ip = a.ifconfig()[0]
        return ip

def client():
    network_use_wlan(True)
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    ai = socket.getaddrinfo("192.168.1.110", 8080)
    print("Address infos:", ai)
    addr = ai[0][-1]

    print("Connecting to:", addr)
    try:
        s.connect(addr)
    except Exception as e:
        s.close()
        print("Connection error:", e)
        return

    for i in range(10):
        message = "K230 TCP client send test {0} \r\n".format(i)
        print("Sending:", message)
        s.sendall(message.encode())
        time.sleep(0.2)

    s.close()
    print("Connection closed.")

client()

3. Running Results and Operation Instructions

1. Open the NetAssist Network Debugging Assistant, configure it as a TCP server, and wait for the connection:

1. Modify the server’s IP and port number in the code:

ai = socket.getaddrinfo("172.16.1.174", 8080)

1. Run the client code, and NetAssist will display the messages sent by the client: