Note

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TCP-Client Example Explanation

Environment Preparation

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

Hardware Connection

• Please ensure that your CanMV development board and computer are connected to the same router or switch via Ethernet cables, forming a local area network.

• Make sure the router or switch is working properly to ensure stable network connectivity.

Disable Firewall

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

Tool Preparation

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

Obtain IP Address

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

Client Code Analysis

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 time-related functions, such as delay (sleep).

Define the Client Function

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

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

Configure the Network Interface

def network_use_wlan(is_wlan=True):
    if is_wlan:
        sta = network.WLAN(0)
        sta.connect("TEST", "12345678")
        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 parameter. The flow is as follows:

1. WLAN Mode:

   • If is_wlan=True, configure the wireless network interface (WLAN) and connect to the Wi-Fi with SSID “TEST” and password “12345678”.

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

2. LAN Mode:

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

Create a Socket

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

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

Get the Server Address and Port

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

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

Connect to the 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.

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, and use the sendall method to ensure each message is completely sent.

Close the Socket

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

• Close the Socket to release resources, indicating that the client ends the connection.

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("TEST", "12345678")
        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()

Running Results and Operation Instructions

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