【test】Socket operation on non-socket 错误出现有两种情况:

如 调用connect socket accept 函数出错,可以 perror(“socket”); perror(“connect”); printf(“%s\n”,strerror(errno));都能打出具体的错误

select 函数再次强调:<0 : 出错返回,=0: 正常,超时返回,就是没有fd可读可写,只针对于非阻塞 >0: 正常返回,而且可以调用FDISSET函数去查fd;

Socket operation on non-socket 错误出现有两种情况:
1. 建立socket:

                 if(listenfd= socket(AF_INET,SOCK_STREAM, 0)==-1){
                      perror("creating socket failed!");
                      exit(-1);
                 }

会造成在bind时出现 Socket operation on non-socket错误
正确的代码应该是:

                  if((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
                        perror("creating socket failed!");
                        exit(-1);
                  }
  2.  accept时:
                 if(connfd=accept(listenfd,(struct sockaddr *)&client_addr,(socklen_t *)&sin_size)==-1){
                      perror("accept error!");
                      exit(-1);
                 }

会造成在recv时出现 Socket operation on non-socket错误
正确代码是:

                 if((connfd=accept(listenfd,(struct sockaddr *)&client_addr,(socklen_t *)&sin_size))==-1){
                         perror("accept error!");
                         exit(-1);
                 }

出现Socket operation on non-socket 错误的原因是:

            if(listenfd= socket(AF_INET,SOCK_STREAM, 0)==-1)
            if(connfd=accept(listenfd,(struct sockaddr *)&client_addr,(socklen_t *)&sin_size)==-1)

原因是fd赋值错误
这两句中缺失了()造成的。赋值符合优先级最低,导致listenfd和connfd在创建/连接成功是为0,不成功时为1

### CAN Communication ACK Error Solution In Controller Area Network (CAN) systems, an acknowledgment (ACK) error occurs when a node does not receive the expected acknowledgment from another node after transmitting a message. This issue can arise due to several reasons including hardware faults, software misconfiguration, or network issues. To address this problem effectively: #### Diagnosing the Issue When encountering ACK errors in CAN communication, one should first verify the physical connections and ensure that all nodes on the bus are properly connected without any breaks or shorts. Additionally, checking for proper termination resistors at both ends of the bus is crucial since missing terminations may lead to signal reflections causing transmission problems[^1]. #### Checking Electrical Characteristics Ensure that electrical characteristics such as voltage levels meet specifications defined by ISO 11898 standard which governs high-speed CAN buses operating up to 1 Mbps. Voltage measurements must fall within specified limits during dominant and recessive states; otherwise, incorrect signaling might occur leading to ACK failures. #### Software Configuration Review Reviewing the configuration settings used across different devices involved in CAN communications helps identify potential mismatches between baud rates or timing parameters set incorrectly among various ECUs participating in conversations over the same medium. Misaligned configurations could result in corrupted frames being sent out resulting in non-receipt acknowledgments. #### Utilizing Diagnostic Tools Utilize diagnostic tools like oscilloscopes along with specialized CAN analyzers capable of capturing real-time traffic patterns while also providing detailed insights into frame structures allowing deeper analysis beyond what simple logic probes offer. These instruments help pinpoint exact locations where errors happen making troubleshooting more efficient. ```python import can def check_can_ack_error(bus_interface): try: # Initialize CAN Bus Interface bus = can.interface.Bus(bustype='socketcan', channel=bus_interface) # Send test message msg = can.Message(arbitration_id=0x7de, data=[0, 25, 0, 1, 3, 1, 4, 1], is_extended_id=False) bus.send(msg) # Listen for response received_msg = bus.recv(timeout=1.0) if received_msg is None: print("No ACK Received!") else: print(f"Message acknowledged: {received_msg}") except Exception as e: print(e) check_can_ack_error('vcan0') ``` --related questions-- 1. What causes common types of errors found in CAN networks besides ACK errors? 2. How do you configure correct termination resistance values for optimal performance in CAN setups? 3. Can improper power supply affect CAN bus operation stability? If yes, how so? 4. Are there specific standards guiding low-speed versus high-speed CAN implementations differently regarding error handling mechanisms? 5. In what scenarios would using a dedicated CAN analyzer provide advantages compared to general-purpose debugging equipment?
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