How to debug network problems in C++ programs?

For cross-platform C++ applications encountering connection issues in Linux, debugging steps include: attaching a debugger to set breakpoints; checking network connections and firewall rules; checking socket options (such as SO_KEEPALIVE); using system calls The tracing tool examines socket calls; enables logging to find exceptions; and compares Windows and Linux versions of networking code to ensure consistency.

#How to debug network problems in a C++ program?

Practice case:

Suppose you have a cross-platform C++ application where the networking code works fine in Windows but has connectivity issues in Linux.

Debugging steps:

1. Attach to the process using the debugger:

• In Windows: Use Visual Studio or other debugger
• In Linux: Use GDB or LLDB

2. Set breakpoints:

• Set breakpoints during network operations (such as connect(), send(), recv()).

3. Check the network connection:

• Use the netstat -an command to check the network connection.
• Check whether the application is blocked by firewall rules.
• Try using tools like Wireshark to sniff network traffic.

4. Check the socket options:

• Use socket options (such as SO_KEEPALIVE) to ensure that the socket Word connections remain active.
• Check the socket timeout value to ensure a reply is received before timing out.

5. Consider system calls:

• Use strace or ltrace system call tracing tools , to trace the system calls executed by the program.
• Check if the socket call failed and what the error code was.

6. Check the logs:

• Enable logging to record network operations and errors.
• Check the logs for exceptions or tips.

7. Compare Windows and Linux code:

• Check if there are any differences between the Windows and Linux versions of the networking code.
• Make sure to use the appropriate API and options for your target platform.

Using the debugger example:

// Windows 中使用 Visual Studio
auto status = ::connect(socket, address.data(), sizeof(address));
if (status == SOCKET_ERROR) {
    // 检查错误代码
    int error = ::WSAGetLastError();
    // 输出错误信息
    std::cerr << "connect() 失败：" << error << std::endl;
    return false;
}

// Linux 中使用 GDB
(gdb) b socket.cpp:24
(gdb) r
(gdb) n

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