Create option for setting and getting the hostname

docs/api.md

@@ -473,6 +473,83 @@ void setup() {
 void loop () {}
 ```
 
+### `Ethernet.setHostName()`
+
+#### Description
+
+Set the hostname of the device. This is used in DHCP requests and responses.
+
+
+#### Syntax
+
+```
+Ethernet.setHostName(hostName)
+
+```
+
+#### Parameters
+- hostName: the hostname of the device (const char*)
+
+#### Returns
+Nothing
+
+#### Example
+
+```
+#include <SPI.h>
+#include <Ethernet.h>
+
+byte mac[] = {0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};
+char hostName[] = "NameOfTheDevice";
+
+void setup() {
+  Ethernet.setHostName(hostName);
+  Ethernet.begin(mac);
+}
+
+void loop () {}
+```
+
+### `Ethernet.getHostName()`
+
+#### Description
+
+Get the hostname of the device. This is used in DHCP requests and responses.
+
+
+#### Syntax
+
+```
+Ethernet.getHostName()
+
+```
+
+#### Parameters
+none
+
+#### Returns
+- hostName: the hostname of the device (const char*)
+
+#### Example
+
+```
+#include <SPI.h>
+#include <Ethernet.h>
+
+byte mac[] = {0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};
+
+void setup() {
+  Ethernet.begin(mac);
+  const char* hostName = Ethernet.getHostName();
+
+  Serial.begin(9600);
+  Serial.print("Host name: ");
+  Serial.println(hostName);
+}
+
+void loop () {}
+```
+
 ### `Ethernet.setGatewayIP()`
 
 #### Description

examples/SetHostName/SetHostName.ino

@@ -0,0 +1,61 @@
+/*
+  Set Host Name
+
+  This example shows you how to set the host name with the Ethernet library.
+
+  Circuit:
+  * Ethernet shield attached to pins 10, 11, 12, 13
+
+  created 28 May 2023
+  by Attila Herczog
+*/
+
+#include <SPI.h>
+#include <Ethernet.h>
+
+// Enter a MAC address for your controller below.
+// Newer Ethernet shields have a MAC address printed on a sticker on the shield
+byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
+
+// Host name to use
+char hostName[] = "ExampleHostName";
+
+void setup()
+{
+  // Open serial communications and wait for port to open:
+  Serial.begin(9600);
+  while (!Serial)
+  {
+    ; // wait for serial port to connect. Needed for native USB port only
+  }
+  Serial.println("Host Name Example");
+
+  // Set the Host Name
+  // Call this function before Ethernet.begin() to set your host name.
+  Ethernet.setHostName(hostName);
+
+  // Start the Ethernet connection and the server:
+  Ethernet.begin(mac);
+
+  // Check for Ethernet hardware present
+  if (Ethernet.hardwareStatus() == EthernetNoHardware)
+  {
+    Serial.println("Ethernet shield was not found.  Sorry, can't run without hardware. :(");
+    while (true)
+    {
+      delay(1); // do nothing, no point running without Ethernet hardware
+    }
+  }
+  if (Ethernet.linkStatus() == LinkOFF)
+  {
+    Serial.println("Ethernet cable is not connected.");
+  }
+
+  Serial.print("My IP is: ");
+  Serial.println(Ethernet.localIP());
+  Serial.print("My host name is: ");
+  Serial.println(Ethernet.getHostName());
+  Serial.println("You can now check your router's DHCP table to see the assigned host name.");
+}
+
+void loop() {}

src/Dhcp.cpp

@@ -6,13 +6,14 @@
 #include "Dhcp.h"
 #include "utility/w5100.h"
 
-int DhcpClass::beginWithDHCP(uint8_t *mac, unsigned long timeout, unsigned long responseTimeout)
+int DhcpClass::beginWithDHCP(uint8_t *mac, const char *hostName, unsigned long timeout, unsigned long responseTimeout)
 {
 	_dhcpLeaseTime=0;
 	_dhcpT1=0;
 	_dhcpT2=0;
 	_timeout = timeout;
 	_responseTimeout = responseTimeout;
+	_dhcpHostName = hostName;
 
 	// zero out _dhcpMacAddr
 	memset(_dhcpMacAddr, 0, 6);
@@ -186,17 +187,16 @@ void DhcpClass::send_DHCP_MESSAGE(uint8_t messageType, uint16_t secondsElapsed)
 	buffer[9] = 0x01;
 	memcpy(buffer + 10, _dhcpMacAddr, 6);
 
-	// OPT - host name
-	buffer[16] = hostName;
-	buffer[17] = strlen(HOST_NAME) + 6; // length of hostname + last 3 bytes of mac address
-	strcpy((char*)&(buffer[18]), HOST_NAME);
+	_dhcpUdpSocket.write(buffer, 16);
 
-	printByte((char*)&(buffer[24]), _dhcpMacAddr[3]);
-	printByte((char*)&(buffer[26]), _dhcpMacAddr[4]);
-	printByte((char*)&(buffer[28]), _dhcpMacAddr[5]);
+	// OPT - host name
+	buffer[0] = hostName;
+	uint8_t hostNameLength = strlen(_dhcpHostName);
+	buffer[1] = hostNameLength;
+	strcpy((char*)&(buffer[2]), _dhcpHostName);
 
 	//put data in W5100 transmit buffer
-	_dhcpUdpSocket.write(buffer, 30);
+	_dhcpUdpSocket.write(buffer, hostNameLength + 2);
 
 	if (messageType == DHCP_REQUEST) {
 		buffer[0] = dhcpRequestedIPaddr;

src/Dhcp.h

@@ -42,7 +42,6 @@
 #define MAGIC_COOKIE		0x63825363
 #define MAX_DHCP_OPT		16
 
-#define HOST_NAME "WIZnet"
 #define DEFAULT_LEASE	(900) //default lease time in seconds
 
 #define DHCP_CHECK_NONE         (0)

src/Ethernet.cpp

@@ -25,6 +25,8 @@
 
 IPAddress EthernetClass::_dnsServerAddress;
 DhcpClass* EthernetClass::_dhcp = NULL;
+bool EthernetClass::_manualHostName = false;
+char EthernetClass::_hostName[HOST_NAME_MAX_LEN] = "";
 
 int EthernetClass::begin(uint8_t *mac, unsigned long timeout, unsigned long responseTimeout)
 {
@@ -38,8 +40,13 @@ int EthernetClass::begin(uint8_t *mac, unsigned long timeout, unsigned long resp
 	W5100.setIPAddress(IPAddress(0,0,0,0).raw_address());
 	SPI.endTransaction();
 
+	// Generate a default host name based on the MAC address if not already set by user
+	if(!_manualHostName) {
+		generateDefaultHostName(mac);
+	}
+
 	// Now try to get our config info from a DHCP server
-	int ret = _dhcp->beginWithDHCP(mac, timeout, responseTimeout);
+	int ret = _dhcp->beginWithDHCP(mac, _hostName, timeout, responseTimeout);
 	if (ret == 1) {
 		// We've successfully found a DHCP server and got our configuration
 		// info, so set things accordingly
@@ -224,6 +231,32 @@ void EthernetClass::setRetransmissionCount(uint8_t num)
 	SPI.endTransaction();
 }
 
+void EthernetClass::generateDefaultHostName(uint8_t *mac) {
+	// Generate a default host name based on the MAC address
+	strcpy_P(_hostName, PSTR(DEFAULT_HOST_NAME));
+
+	// Append last 3 bytes of MAC address to the name
+	PGM_P hexChars = PSTR("0123456789ABCDEF");
+	for (int i = 0; i <= 2; i++)
+	{
+		_hostName[DEFAULT_HOST_NAME_LENGTH + i * 2] = pgm_read_byte_near(hexChars + (mac[3 + i] >> 4));
+		_hostName[DEFAULT_HOST_NAME_LENGTH + i * 2 + 1] = pgm_read_byte_near(hexChars + (mac[3 + i] & 0x0F));
+	}
+	_hostName[DEFAULT_HOST_NAME_LENGTH + 6] = '\0';
+}
+
+void EthernetClass::setHostName(const char *dhcpHost) {
+	// Copy the host name and ensure it is null terminated
+	strncpy(_hostName, dhcpHost, HOST_NAME_MAX_LEN);
+    _hostName[HOST_NAME_MAX_LEN - 1] = '\0';
+
+	// Indicate that a host name has been set manually
+	_manualHostName = true;
+}
+
+char* EthernetClass::getHostName() {
+	return _hostName;
+}
 
 
 

src/Ethernet.h

@@ -53,6 +53,10 @@
 #include "Server.h"
 #include "Udp.h"
 
+#define DEFAULT_HOST_NAME "WIZnet"
+#define DEFAULT_HOST_NAME_LENGTH (sizeof(DEFAULT_HOST_NAME) - 1)
+#define HOST_NAME_MAX_LEN 20 // Max 30 or change the DHCP local buffer size
+
 enum EthernetLinkStatus {
 	Unknown,
 	LinkON,
@@ -75,6 +79,8 @@ class EthernetClass {
 private:
 	static IPAddress _dnsServerAddress;
 	static DhcpClass* _dhcp;
+	static char _hostName[HOST_NAME_MAX_LEN];
+	static bool _manualHostName;
 public:
 	// Initialise the Ethernet shield to use the provided MAC address and
 	// gain the rest of the configuration through DHCP.
@@ -104,6 +110,8 @@ class EthernetClass {
 	void setDnsServerIP(const IPAddress dns_server) { _dnsServerAddress = dns_server; }
 	void setRetransmissionTimeout(uint16_t milliseconds);
 	void setRetransmissionCount(uint8_t num);
+  	void setHostName(const char *hostName);
+	char* getHostName();
 
 	friend class EthernetClient;
 	friend class EthernetServer;
@@ -142,6 +150,7 @@ class EthernetClass {
 	static bool socketSendUDP(uint8_t s);
 	// Initialize the "random" source port number
 	static void socketPortRand(uint16_t n);
+	static void generateDefaultHostName(uint8_t *mac);
 };
 
 extern EthernetClass Ethernet;
@@ -275,6 +284,7 @@ class DhcpClass {
 	uint32_t _dhcpInitialTransactionId;
 	uint32_t _dhcpTransactionId;
 	uint8_t  _dhcpMacAddr[6];
+	const char* _dhcpHostName;
 #ifdef __arm__
 	uint8_t  _dhcpLocalIp[4] __attribute__((aligned(4)));
 	uint8_t  _dhcpSubnetMask[4] __attribute__((aligned(4)));
@@ -312,7 +322,7 @@ class DhcpClass {
 	IPAddress getDhcpServerIp();
 	IPAddress getDnsServerIp();
 
-	int beginWithDHCP(uint8_t *, unsigned long timeout = 60000, unsigned long responseTimeout = 4000);
+	int beginWithDHCP(uint8_t *, const char *hostName, unsigned long timeout = 60000, unsigned long responseTimeout = 4000);
 	int checkLease();
 };