Network get_use_address() Optimization

Nov 20, 2025

J. Nick Koston

ESPHome Maintainer

The network::get_use_address() function has been optimized to return const char* instead of const std::string& to reduce memory overhead. This eliminates unnecessary string object storage when accessing the device’s network address.

This is a breaking change for external components that call network::get_use_address() in ESPHome 2025.11.0 and later.

What needs to change

External components must remove .c_str() calls when using get_use_address():

// ❌ Before 2025.11
ESP_LOGCONFIG(TAG, "  Address: %s:%u",
              esphome::network::get_use_address().c_str(), this->port_);

// ✅ After 2025.11
ESP_LOGCONFIG(TAG, "  Address: %s:%u",
              esphome::network::get_use_address(), this->port_);

Compilation errors

External components using .c_str() will fail with:

error: member reference base type 'const char *' is not a structure or union
  esphome::network::get_use_address().c_str()
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~

The fix is simple: remove .c_str().

Common usage patterns

Logging (most common)

// Before 2025.11
ESP_LOGD(TAG, "Connecting to %s",
         esphome::network::get_use_address().c_str());

// After 2025.11
ESP_LOGD(TAG, "Connecting to %s",
         esphome::network::get_use_address());

Storing the address

If you need to store the address in a std::string:

// Before 2025.11
std::string address = esphome::network::get_use_address();

// After 2025.11 (still works - implicit conversion)
std::string address = esphome::network::get_use_address();

// After 2025.11 (more efficient if you don't need mutation)
const char *address = esphome::network::get_use_address();

Passing to functions

// Before 2025.11
this->client_->connect(esphome::network::get_use_address().c_str(), port);

// After 2025.11
this->client_->connect(esphome::network::get_use_address(), port);

Supporting multiple ESPHome versions

If your external component needs to support both old and new ESPHome versions:

#if ESPHOME_VERSION_CODE >= VERSION_CODE(2025, 11, 0)
  ESP_LOGCONFIG(TAG, "  Address: %s:%u",
                esphome::network::get_use_address(), this->port_);
#else
  ESP_LOGCONFIG(TAG, "  Address: %s:%u",
                esphome::network::get_use_address().c_str(), this->port_);
#endif

Cleaner version with macro

For components with many uses:

#if ESPHOME_VERSION_CODE >= VERSION_CODE(2025, 11, 0)
  #define GET_USE_ADDRESS() esphome::network::get_use_address()
#else
  #define GET_USE_ADDRESS() esphome::network::get_use_address().c_str()
#endif

// Then use throughout your code:
ESP_LOGCONFIG(TAG, "  Address: %s:%u", GET_USE_ADDRESS(), this->port_);

Affected components

This change affects the following network components:

• wifi - wifi::get_use_address()
• ethernet - ethernet::get_use_address()
• openthread - openthread::get_use_address()

All three now return const char* instead of const std::string&.

Note: esphome::network::get_use_address() is a wrapper function that delegates to the appropriate component-specific function (wifi::get_use_address(), ethernet::get_use_address(), or openthread::get_use_address()) depending on your network configuration. Most external components should use the network:: wrapper for generic code. Only use component-specific functions if your code explicitly depends on a particular network type.

Why this change

The previous implementation stored the address internally as a std::string and returned a reference to it. This meant:

1. Unnecessary string object overhead - The address was stored as a std::string, even though it is typically a static configuration value set once during setup
2. Extra memory usage - The std::string object itself uses heap memory plus object overhead (typically 24-32 bytes)
3. API complexity - Callers needed to use .c_str() to access the raw address for logging, even though no conversion or copy was performed

By returning const char* directly and storing the address as a pointer to flash memory (RODATA):

• Zero string object overhead - No std::string objects are created or stored for the address
• Simpler API - The address can be used directly in logging and C-style string functions
• Memory savings - Eliminates the std::string overhead, saving 32-72 bytes of RAM per network component

Real-world example

Here’s the fix applied to esphome-stream-server:

void StreamServerComponent::dump_config() {
    ESP_LOGCONFIG(TAG, "Stream Server:");
#if ESPHOME_VERSION_CODE >= VERSION_CODE(2025, 11, 0)
    ESP_LOGCONFIG(TAG, "  Address: %s:%u",
                  esphome::network::get_use_address(), this->port_);
#else
    ESP_LOGCONFIG(TAG, "  Address: %s:%u",
                  esphome::network::get_use_address().c_str(), this->port_);
#endif
    // ... rest of dump_config
}

Finding code that needs updates

# Find uses of get_use_address().c_str()
grep -rn "get_use_address()\.c_str()" your_component/

# Check for all get_use_address() calls to review
grep -rn "get_use_address()" your_component/

Reference Pull Request

• esphome/esphome#11707

Questions?

If you have questions about migrating your external component, please ask in:

• ESPHome Discord - #devs channel
• ESPHome GitHub Discussions

Light State Callbacks: Listener Pattern Migration

Climate Entity Class: FiniteSetMask and Flash Storage Optimizations