def read_registers(self, start_addr, count): request = struct.pack('>HHHH', 0x0001, start_addr, count, 0x0000) self.socket.send(request) response = self.socket.recv(1024) return struct.unpack_from('>' + 'H' * count, response, offset=9) def write_register(self, addr, value): request = struct.pack('>HHH', 0x0006, addr, value) self.socket.send(request) response = self.socket.recv(1024) return struct.unpack_from('>HH', response, offset=9)

这是一个使用Python语言操作Modbus协议的示例代码。其中包括两个方法：

1. `read_registers(self, start_addr, count)`：该方法用于读取Modbus设备中的寄存器数据。方法中首先根据`start_addr`和`count`参数构建一个读取请求，然后通过socket发送请求，等待设备响应并接收响应数据。最后，使用`struct.unpack_from()`函数将响应数据解包成一个长度为`count`的整数列表并返回。

2. `write_register(self, addr, value)`：该方法用于向Modbus设备中写入寄存器数据。方法中首先根据`addr`和`value`参数构建一个写入请求，然后通过socket发送请求，等待设备响应并接收响应数据。最后，使用`struct.unpack_from()`函数将响应数据解包成一个长度为2的整数元组并返回。

这些方法中的`struct.pack()`和`struct.unpack_from()`函数用于将数据打包成二进制流或从二进制流中解包出数据。这些函数的具体用法可以参考Python标准库文档。

相关问题

import concurrent.futures import time import logging import socket import struct import binascii # modbus tcp client class ModbusTCPClient: def __init__(self, ip, port): self.ip = ip self.port = port self.socket = None def connect(self): self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) self.socket.connect((self.ip, self.port)) def disconnect(self): self.socket.close() self.socket = None def read_registers(self, start_addr, count): request = struct.pack('>HHHH', 0x0001, start_addr, count, 0x0000) self.socket.send(request) response = self.socket.recv(1024) return struct.unpack_from('>' + 'H' * count, response, offset=9) def write_register(self, addr, value): request = struct.pack('>HHH', 0x0006, addr, value) self.socket.send(request) response = self.socket.recv(1024) return struct.unpack_from('>HH', response, offset=9) # worker function for thread pool def worker(ip, port, start_addr, count): client = ModbusTCPClient(ip, port) client.connect() try: # read registers values = client.read_registers(start_addr, count) logging.info('ip=%s, values=%s', ip, values) # write a value client.write_register(start_addr, 0x1234) except Exception as e: logging.error('ip=%s, error=%s', ip, str(e)) finally: client.disconnect() # main function def main(): # configure logging logging.basicConfig(level=logging.INFO, format='%(asctime)s %(levelname)s %(message)s') # list of modbus tcp devices devices = [ {'ip': '127.0.0.1', 'port': 502, 'start_addr': 0, 'count': 2}, {'ip': '127.0.0.1', 'port': 503, 'start_addr': 2, 'count': 2}, {'ip': '127.0.0.1', 'port': 504, 'start_addr': 4, 'count': 2}, ] # create thread pool with concurrent.futures.ThreadPoolExecutor(max_workers=len(devices)) as executor: # submit tasks to thread pool futures = [executor.submit(worker, device['ip'], device['port'], device['start_addr'], device['count']) for device in devices] # wait for tasks to complete for future in concurrent.futures.as_completed(futures): try: future.result() except Exception as e: logging.error('error=%s', str(e)) # entry point if __name__ == '__main__': main() 数据包多少

根据代码，数据包的大小是13个字节。对于读取寄存器的请求，使用了struct.pack('>HHHH', 0x0001, start_addr, count, 0x0000)打包成13个字节的请求数据包，其中'>HHHH'表示4个大端无符号short类型数据。对于写入寄存器的请求，使用了struct.pack('>HHH', 0x0006, addr, value)打包成9个字节的请求数据包，其中'>HHH'表示3个大端无符号short类型数据。因此，数据包的大小是13个字节或9个字节，取决于请求类型。

void readAI(modbus_t *ctx) { int i, j, k, tmp; unsigned long YrMin; unsigned short YrMs; SOEINFO Soeinfo; UBYTE ClockArray[9]; struct itimerspec timerValues; struct itimerspec timerValuesold; timerValues.it_value.tv_sec = 0; timerValues.it_value.tv_nsec = 0; timerValues.it_interval.tv_sec = 0; timerValues.it_interval.tv_nsec = 0; timer_settime(AIcmdflag.timer, 0, &timerValues, &timerValuesold); printf("readAI.........\n"); // printf("AI.timer time %d %d \n",timerValuesold.it_value.tv_sec,timerValuesold.it_interval.tv_sec); int StartIndex = 0; int RespondAddr = 0; int SaveIndex = 0; int RespondValue = 0; int16_t val[1024]; for (i = 0; i < modbusRTU.RTUnum; i++) { modbus_set_slave(ctx, modbusRTU.RTU[i]); for (j = 0; j < 3; j++) { if (modbus_read_registers(ctx, StartIndex, 17, val) >= 0) { SaveDiValue(modbusRTU.RTU[i] - 1, 1); if (RtuStatu[i] == 0) { printf("[SF266F]:线路%d上线\n", modbusRTU.RTU[i]); Soeinfo.Value = 1; Soeinfo.Index = modbusRTU.RTU[i] - 1; GetCurrentTime(ClockArray); ArraryToRTC(ClockArray, (PDWORD)&Soeinfo.minutes, (PWORD)&Soeinfo.msec); SendSoeMsg(&Soeinfo); RtuStatu[i] = 1; } for (k = 0; k < 17; k++) { SaveAiValue(k + (modbusRTU.RTU[i] - 1) * 17, val[k] * 1000); if (printflag == 255) { printf("线路号：%d,SaveAiValue index = %d , value = %d !\n", modbusRTU.RTU[i], k + (modbusRTU.RTU[i] - 1) * 17, val[k]); } } break; } else { if (errno == EINTR) { printf("stoped by singal"); } } usleep(100000); } if (j >= 3) { SaveDiValue(modbusRTU.RTU[i] - 1, 0); if (RtuStatu[i] == 1) { printf("[SF266F]:线路%d下线\n", modbusRTU.RTU[i]); Soeinfo.Value = 0; Soeinfo.Index = modbusRTU.RTU[i] - 1; GetCurrentTime(ClockArray); ArraryToRTC(ClockArray, (PDWORD)&Soeinfo.minutes, (PWORD)&Soeinfo.msec); SendSoeMsg(&Soeinfo); RtuStatu[i] = 0; } printf("[ST266F]:RTU %d is offline\n", modbusRTU.RTU[i]); } } timerValuesold.it_value.tv_sec = timerValuesold.it_interval.tv_sec; timerValuesold.it_value.tv_nsec = timerValuesold.it_interval.tv_nsec; timer_settime(AIcmdflag.timer, 0, &timerValuesold, NULL); // printf("AIcmdflag.timer %x time %d\n",AIcmdflag.timer,timerValuesold.it_interval.tv_sec); } // 修改时间 // modbus_write_registers(modbus_t *ctx, int addr, int nb, const uint16_t *src) 功能码0x10

这段代码看起来是一个 C 语言程序，使用了 libmodbus 库进行 Modbus RTU 通信，实现了读取多个设备的 AI 值，并将其保存到数组中。其中，每次读取都会尝试三次，如果三次都读取失败，则将该设备的状态设置为下线，并发送 SOE 消息。此外，代码中还有一个修改时间的函数，使用了功能码 0x10 进行写入操作。