BeagleBone Black与PC的TCP/IP通信实现及运行咨询

一、如何正确运行BeagleBone端的客户端程序 #

Let’s walk through getting your client up and running on the BeagleBone Black (BBB) step by step:

1. Confirm Network Connectivity First

   • SSH into your BBB and run ping 192.168.1.20 to make sure it can reach your PC server. If the ping fails, double-check your Ethernet cable and verify both devices are on the same subnet with the correct static IPs.

2. Transfer the Client Code to BBB

   • Use scp from your PC to send the client.cpp file to the BBB. Assuming you’re using the default Debian username debian, run this command on your PC:

     scp client.cpp debian@192.168.1.15:/home/debian/
     

   • Alternatively, you can create/edit the file directly on the BBB via SSH using nano client.cpp.

3. Fix Critical Gaps in Client Code

   • Your client.cpp is missing essential header files and the error function that’s defined in your server code. Add these at the top of client.cpp:

     #include <iostream>
     #include <netinet/in.h>
     #include <arpa/inet.h>
     #include <errno.h>
     #include <string.h>
     #include <unistd.h>
     #include <stdio.h>
     #include <stdlib.h>
     #include <sys/socket.h>
     #include <sys/types.h>
     #include <netdb.h> // Required for gethostbyname()
     
     using namespace std;
     
     void error(const char *msg) {
         perror(msg);
         exit(1);
     }
     

4. Compile the Client on BBB

   • In your SSH session, navigate to the directory where client.cpp is stored, then compile it with:

     g++ client.cpp -o Client -Wall
     

   • The -Wall flag enables warning messages to catch small issues you might miss otherwise.

5. Launch the Client

   • Run the compiled client, passing your PC’s IP address (192.168.1.20) and the server port (20001) as arguments:

     ./Client 192.168.1.20 20001
     

   • You’ll see the prompt Please enter the message: — type your text and hit enter, and it should be sent to your PC server immediately.

二、代码中的潜在问题 #

Let’s break down areas in both server and client code that could cause issues or be improved:

Client.cpp Issues #

• Outdated Host Lookup: gethostbyname() is deprecated, doesn’t support IPv6, and isn’t thread-safe. Replace it with getaddrinfo() for modern, reliable host resolution.
• Unwanted Newline in Messages: fgets() includes the trailing newline character from your input. If you don’t want this sent to the server, add a line to strip it:

  buffer[strcspn(buffer, "\n")] = '\0';
  

• Incomplete Error Handling: You check for negative return values from write() and read(), but you don’t handle cases where these functions return 0 (which means the remote end closed the connection gracefully).

Server.cpp Issues #

• Redundant Port Macro: You defined #define PORT 20001 but never use it — the port is fetched from argv[1] instead. Remove the unused macro to clean up the code.
• Single Connection Limit: Your server only handles one client connection and then exits. To support multiple concurrent clients, use multithreading or fork() to spawn a new process for each incoming connection.
• Incorrect Send Length: The string "Hello, world!\n" is 14 characters long (including the newline), but you’re sending only 13 bytes. This means the final newline won’t be transmitted. Update the send call to:

  send(newsockfd, "Hello, world!\n", 14, 0);
  

• Unused Buffer Size Macro: SERVER_BUFFER_SIZE is defined but not used (you’re using a 256-byte buffer instead). Align these to avoid confusion.
• No Persistent Connection Loop: After handling one client, the server closes both sockets and exits. Wrap the accept() and subsequent logic in a while(1) loop to keep the server running and accept new connections.

内容的提问来源于stack exchange，提问作者ClaudiaGR