diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..14012d8
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,47 @@
+set(headers
+    src/SocketIOclient.h
+    src/WebSockets.h
+    src/WebSockets4WebServer.h
+    src/WebSocketsClient.h
+    src/WebSocketsServer.h
+    src/WebSocketsVersion.h
+    src/libb64/cdecode_inc.h
+    src/libb64/cencode_inc.h
+    src/libsha1/libsha1.h
+)
+
+set(sources
+    src/SocketIOclient.cpp
+    src/WebSockets.cpp
+    src/WebSocketsClient.cpp
+    src/WebSocketsServer.cpp
+    src/libb64/cdecode.c
+    src/libb64/cencode.c
+    src/libsha1/libsha1.c
+)
+
+set(dependencies
+)
+
+idf_component_register(
+    INCLUDE_DIRS
+        src
+    SRCS
+        ${headers}
+        ${sources}
+    REQUIRES
+        ${dependencies}
+)
+
+target_compile_options(${COMPONENT_TARGET}
+    PUBLIC
+        -DESP32
+        -DWEBSOCKETS_NETWORK_TYPE=NETWORK_ESP32
+    PRIVATE
+        -fstack-reuse=all
+        -fstack-protector-all
+        -Wno-unused-function
+        -Wno-deprecated-declarations
+        -Wno-missing-field-initializers
+        -Wno-parentheses
+)
diff --git a/src/SocketIOclient.cpp b/src/SocketIOclient.cpp
index a06efa2..72a6dd4 100644
--- a/src/SocketIOclient.cpp
+++ b/src/SocketIOclient.cpp
@@ -5,9 +5,12 @@
  *      Author: links
  */
 
+#include "SocketIOclient.h"
+
+#include <string>
+
 #include "WebSockets.h"
 #include "WebSocketsClient.h"
-#include "SocketIOclient.h"
 
 SocketIOclient::SocketIOclient() {
 }
@@ -21,7 +24,7 @@ void SocketIOclient::begin(const char * host, uint16_t port, const char * url, c
     initClient();
 }
 
-void SocketIOclient::begin(String host, uint16_t port, String url, String protocol) {
+void SocketIOclient::begin(std::string host, uint16_t port, std::string url, std::string protocol) {
     WebSocketsClient::beginSocketIO(host, port, url, protocol);
     WebSocketsClient::enableHeartbeat(60 * 1000, 90 * 1000, 5);
     initClient();
@@ -33,7 +36,7 @@ void SocketIOclient::beginSSL(const char * host, uint16_t port, const char * url
     initClient();
 }
 
-void SocketIOclient::beginSSL(String host, uint16_t port, String url, String protocol) {
+void SocketIOclient::beginSSL(std::string host, uint16_t port, std::string url, std::string protocol) {
     WebSocketsClient::beginSocketIOSSL(host, port, url, protocol);
     WebSocketsClient::enableHeartbeat(60 * 1000, 90 * 1000, 5);
     initClient();
@@ -131,7 +134,7 @@ bool SocketIOclient::send(socketIOmessageType_t type, const char * payload, size
     return send(type, (uint8_t *)payload, length);
 }
 
-bool SocketIOclient::send(socketIOmessageType_t type, String & payload) {
+bool SocketIOclient::send(socketIOmessageType_t type, std::string & payload) {
     return send(type, (uint8_t *)payload.c_str(), payload.length());
 }
 
@@ -159,7 +162,7 @@ bool SocketIOclient::sendEVENT(const char * payload, size_t length) {
     return sendEVENT((uint8_t *)payload, length);
 }
 
-bool SocketIOclient::sendEVENT(String & payload) {
+bool SocketIOclient::sendEVENT(std::string & payload) {
     return sendEVENT((uint8_t *)payload.c_str(), payload.length());
 }
 
diff --git a/src/SocketIOclient.h b/src/SocketIOclient.h
index 6deb168..5014f52 100644
--- a/src/SocketIOclient.h
+++ b/src/SocketIOclient.h
@@ -8,6 +8,8 @@
 #ifndef SOCKETIOCLIENT_H_
 #define SOCKETIOCLIENT_H_
 
+#include <string>
+
 #include "WebSockets.h"
 
 #define EIO_HEARTBEAT_INTERVAL 20000
@@ -47,11 +49,11 @@ class SocketIOclient : protected WebSocketsClient {
     virtual ~SocketIOclient(void);
 
     void begin(const char * host, uint16_t port, const char * url = "/socket.io/?EIO=3", const char * protocol = "arduino");
-    void begin(String host, uint16_t port, String url = "/socket.io/?EIO=3", String protocol = "arduino");
+    void begin(std::string host, uint16_t port, std::string url = "/socket.io/?EIO=3", std::string protocol = "arduino");
 
 #ifdef HAS_SSL
     void beginSSL(const char * host, uint16_t port, const char * url = "/socket.io/?EIO=3", const char * protocol = "arduino");
-    void beginSSL(String host, uint16_t port, String url = "/socket.io/?EIO=3", String protocol = "arduino");
+    void beginSSL(std::string host, uint16_t port, std::string url = "/socket.io/?EIO=3", std::string protocol = "arduino");
 #ifndef SSL_AXTLS
     void beginSSLWithCA(const char * host, uint16_t port, const char * url = "/socket.io/?EIO=3", const char * CA_cert = NULL, const char * protocol = "arduino");
     void beginSSLWithCA(const char * host, uint16_t port, const char * url = "/socket.io/?EIO=3", BearSSL::X509List * CA_cert = NULL, const char * protocol = "arduino");
@@ -67,13 +69,13 @@ class SocketIOclient : protected WebSocketsClient {
     bool sendEVENT(const uint8_t * payload, size_t length = 0);
     bool sendEVENT(char * payload, size_t length = 0, bool headerToPayload = false);
     bool sendEVENT(const char * payload, size_t length = 0);
-    bool sendEVENT(String & payload);
+    bool sendEVENT(std::string & payload);
 
     bool send(socketIOmessageType_t type, uint8_t * payload, size_t length = 0, bool headerToPayload = false);
     bool send(socketIOmessageType_t type, const uint8_t * payload, size_t length = 0);
     bool send(socketIOmessageType_t type, char * payload, size_t length = 0, bool headerToPayload = false);
     bool send(socketIOmessageType_t type, const char * payload, size_t length = 0);
-    bool send(socketIOmessageType_t type, String & payload);
+    bool send(socketIOmessageType_t type, std::string & payload);
 
     void loop(void);
 
diff --git a/src/WebSockets.cpp b/src/WebSockets.cpp
index ef8224c..a237399 100644
--- a/src/WebSockets.cpp
+++ b/src/WebSockets.cpp
@@ -24,6 +24,8 @@
 
 #include "WebSockets.h"
 
+#include <string>
+
 #ifdef ESP8266
 #include <core_esp8266_features.h>
 #endif
@@ -535,15 +537,15 @@ void WebSockets::handleWebsocketPayloadCb(WSclient_t * client, bool ok, uint8_t
 
 /**
  * generate the key for Sec-WebSocket-Accept
- * @param clientKey String
- * @return String Accept Key
+ * @param clientKey std::string
+ * @return std::string Accept Key
  */
-String WebSockets::acceptKey(String & clientKey) {
+std::string WebSockets::acceptKey(std::string & clientKey) {
     uint8_t sha1HashBin[20] = { 0 };
 #ifdef ESP8266
     sha1(clientKey + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11", &sha1HashBin[0]);
 #elif defined(ESP32)
-    String data = clientKey + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
+    std::string data = clientKey + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
     esp_sha(SHA1, (unsigned char *)data.c_str(), data.length(), &sha1HashBin[0]);
 #else
     clientKey += "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
@@ -553,7 +555,7 @@ String WebSockets::acceptKey(String & clientKey) {
     SHA1Final(&sha1HashBin[0], &ctx);
 #endif
 
-    String key = base64_encode(sha1HashBin, 20);
+    std::string key = base64_encode(sha1HashBin, 20);
     key.trim();
 
     return key;
@@ -563,9 +565,9 @@ String WebSockets::acceptKey(String & clientKey) {
  * base64_encode
  * @param data uint8_t *
  * @param length size_t
- * @return base64 encoded String
+ * @return base64 encoded std::string
  */
-String WebSockets::base64_encode(uint8_t * data, size_t length) {
+std::string WebSockets::base64_encode(uint8_t * data, size_t length) {
     size_t size   = ((length * 1.6f) + 1);
     char * buffer = (char *)malloc(size);
     if(buffer) {
@@ -574,11 +576,11 @@ String WebSockets::base64_encode(uint8_t * data, size_t length) {
         int len = base64_encode_block((const char *)&data[0], length, &buffer[0], &_state);
         len     = base64_encode_blockend((buffer + len), &_state);
 
-        String base64 = String(buffer);
+        std::string base64 = std::string(buffer);
         free(buffer);
         return base64;
     }
-    return String("-FAIL-");
+    return std::string("-FAIL-");
 }
 
 /**
diff --git a/src/WebSockets.h b/src/WebSockets.h
index b182bd5..800fa9e 100644
--- a/src/WebSockets.h
+++ b/src/WebSockets.h
@@ -25,12 +25,14 @@
 #ifndef WEBSOCKETS_H_
 #define WEBSOCKETS_H_
 
+#include <string>
+
 #ifdef STM32_DEVICE
 #include <application.h>
 #define bit(b) (1UL << (b))    // Taken directly from Arduino.h
 #else
-#include <Arduino.h>
-#include <IPAddress.h>
+//#include <Arduino.h>
+//#include <IPAddress.h>
 #endif
 
 #ifdef ARDUINO_ARCH_AVR
@@ -186,8 +188,8 @@
 
 #elif(WEBSOCKETS_NETWORK_TYPE == NETWORK_ESP32)
 
-#include <WiFi.h>
-#include <WiFiClientSecure.h>
+//#include <WiFi.h>
+//#include <WiFiClientSecure.h>
 #define SSL_AXTLS
 #define WEBSOCKETS_NETWORK_CLASS WiFiClient
 #define WEBSOCKETS_NETWORK_SSL_CLASS WiFiClientSecure
@@ -284,28 +286,28 @@ typedef struct {
     WEBSOCKETS_NETWORK_SSL_CLASS * ssl;
 #endif
 
-    String cUrl;           ///< http url
+    std::string cUrl;           ///< http url
     uint16_t cCode = 0;    ///< http code
 
     bool cIsClient    = false;    ///< will be used for masking
     bool cIsUpgrade   = false;    ///< Connection == Upgrade
     bool cIsWebsocket = false;    ///< Upgrade == websocket
 
-    String cSessionId;        ///< client Set-Cookie (session id)
-    String cKey;              ///< client Sec-WebSocket-Key
-    String cAccept;           ///< client Sec-WebSocket-Accept
-    String cProtocol;         ///< client Sec-WebSocket-Protocol
-    String cExtensions;       ///< client Sec-WebSocket-Extensions
+    std::string cSessionId;        ///< client Set-Cookie (session id)
+    std::string cKey;              ///< client Sec-WebSocket-Key
+    std::string cAccept;           ///< client Sec-WebSocket-Accept
+    std::string cProtocol;         ///< client Sec-WebSocket-Protocol
+    std::string cExtensions;       ///< client Sec-WebSocket-Extensions
     uint16_t cVersion = 0;    ///< client Sec-WebSocket-Version
 
     uint8_t cWsRXsize = 0;                            ///< State of the RX
     uint8_t cWsHeader[WEBSOCKETS_MAX_HEADER_SIZE];    ///< RX WS Message buffer
     WSMessageHeader_t cWsHeaderDecode;
 
-    String base64Authorization;    ///< Base64 encoded Auth request
-    String plainAuthorization;     ///< Base64 encoded Auth request
+    std::string base64Authorization;    ///< Base64 encoded Auth request
+    std::string plainAuthorization;     ///< Base64 encoded Auth request
 
-    String extraHeaders;
+    std::string extraHeaders;
 
     bool cHttpHeadersValid = false;    ///< non-websocket http header validity indicator
     size_t cMandatoryHeadersCount;     ///< non-websocket mandatory http headers present count
@@ -318,7 +320,7 @@ typedef struct {
     uint8_t pongTimeoutCount       = 0;    // current pong timeout count
 
 #if(WEBSOCKETS_NETWORK_TYPE == NETWORK_ESP8266_ASYNC)
-    String cHttpLine;    ///< HTTP header lines
+    std::string cHttpLine;    ///< HTTP header lines
 #endif
 
 } WSclient_t;
@@ -350,8 +352,8 @@ class WebSockets {
     void handleWebsocketCb(WSclient_t * client);
     void handleWebsocketPayloadCb(WSclient_t * client, bool ok, uint8_t * payload);
 
-    String acceptKey(String & clientKey);
-    String base64_encode(uint8_t * data, size_t length);
+    std::string acceptKey(std::string & clientKey);
+    std::string base64_encode(uint8_t * data, size_t length);
 
     bool readCb(WSclient_t * client, uint8_t * out, size_t n, WSreadWaitCb cb);
     virtual size_t write(WSclient_t * client, uint8_t * out, size_t n);
diff --git a/src/WebSockets4WebServer.h b/src/WebSockets4WebServer.h
index ba2b020..6c962d9 100644
--- a/src/WebSockets4WebServer.h
+++ b/src/WebSockets4WebServer.h
@@ -25,6 +25,8 @@
 #ifndef __WEBSOCKETS4WEBSERVER_H
 #define __WEBSOCKETS4WEBSERVER_H
 
+#include <string>
+
 #include <WebSocketsServer.h>
 #include <ESP8266WebServer.h>
 
@@ -32,15 +34,15 @@
 
 class WebSockets4WebServer : public WebSocketsServerCore {
   public:
-    WebSockets4WebServer(const String & origin = "", const String & protocol = "arduino")
+    WebSockets4WebServer(const std::string & origin = "", const std::string & protocol = "arduino")
         : WebSocketsServerCore(origin, protocol) {
         begin();
     }
 
-    ESP8266WebServer::HookFunction hookForWebserver(const String & wsRootDir, WebSocketServerEvent event) {
+    ESP8266WebServer::HookFunction hookForWebserver(const std::string & wsRootDir, WebSocketServerEvent event) {
         onEvent(event);
 
-        return [&, wsRootDir](const String & method, const String & url, WiFiClient * tcpClient, ESP8266WebServer::ContentTypeFunction contentType) {
+        return [&, wsRootDir](const std::string & method, const std::string & url, WiFiClient * tcpClient, ESP8266WebServer::ContentTypeFunction contentType) {
             (void)contentType;
 
             if(!(method == "GET" && url.indexOf(wsRootDir) == 0)) {
@@ -55,7 +57,7 @@ class WebSockets4WebServer : public WebSocketsServerCore {
 
             if(client) {
                 // give "GET <url>"
-                String headerLine;
+                std::string headerLine;
                 headerLine.reserve(url.length() + 5);
                 headerLine = "GET ";
                 headerLine += url;
diff --git a/src/WebSocketsClient.cpp b/src/WebSocketsClient.cpp
index e3519c8..97334c0 100644
--- a/src/WebSocketsClient.cpp
+++ b/src/WebSocketsClient.cpp
@@ -22,9 +22,12 @@
  *
  */
 
-#include "WebSockets.h"
 #include "WebSocketsClient.h"
 
+#include <string>
+
+#include "WebSockets.h"
+
 WebSocketsClient::WebSocketsClient() {
     _cbEvent             = NULL;
     _client.num          = 0;
@@ -90,7 +93,7 @@ void WebSocketsClient::begin(const char * host, uint16_t port, const char * url,
     DEBUG_WEBSOCKETS("[WS-Client] Websocket Version: " WEBSOCKETS_VERSION "\n");
 }
 
-void WebSocketsClient::begin(String host, uint16_t port, String url, String protocol) {
+void WebSocketsClient::begin(std::string host, uint16_t port, std::string url, std::string protocol) {
     begin(host.c_str(), port, url.c_str(), protocol.c_str());
 }
 
@@ -107,7 +110,7 @@ void WebSocketsClient::beginSSL(const char * host, uint16_t port, const char * u
     _CA_cert      = NULL;
 }
 
-void WebSocketsClient::beginSSL(String host, uint16_t port, String url, String fingerprint, String protocol) {
+void WebSocketsClient::beginSSL(std::string host, uint16_t port, std::string url, std::string fingerprint, std::string protocol) {
     beginSSL(host.c_str(), port, url.c_str(), fingerprint.c_str(), protocol.c_str());
 }
 
@@ -153,7 +156,7 @@ void WebSocketsClient::beginSocketIO(const char * host, uint16_t port, const cha
     _client.isSocketIO = true;
 }
 
-void WebSocketsClient::beginSocketIO(String host, uint16_t port, String url, String protocol) {
+void WebSocketsClient::beginSocketIO(std::string host, uint16_t port, std::string url, std::string protocol) {
     beginSocketIO(host.c_str(), port, url.c_str(), protocol.c_str());
 }
 
@@ -165,7 +168,7 @@ void WebSocketsClient::beginSocketIOSSL(const char * host, uint16_t port, const
     _fingerprint       = SSL_FINGERPRINT_NULL;
 }
 
-void WebSocketsClient::beginSocketIOSSL(String host, uint16_t port, String url, String protocol) {
+void WebSocketsClient::beginSocketIOSSL(std::string host, uint16_t port, std::string url, std::string protocol) {
     beginSocketIOSSL(host.c_str(), port, url.c_str(), protocol.c_str());
 }
 
@@ -320,7 +323,7 @@ bool WebSocketsClient::sendTXT(const char * payload, size_t length) {
     return sendTXT((uint8_t *)payload, length);
 }
 
-bool WebSocketsClient::sendTXT(String & payload) {
+bool WebSocketsClient::sendTXT(std::string & payload) {
     return sendTXT((uint8_t *)payload.c_str(), payload.length());
 }
 
@@ -365,7 +368,7 @@ bool WebSocketsClient::sendPing(uint8_t * payload, size_t length) {
     return false;
 }
 
-bool WebSocketsClient::sendPing(String & payload) {
+bool WebSocketsClient::sendPing(std::string & payload) {
     return sendPing((uint8_t *)payload.c_str(), payload.length());
 }
 
@@ -386,7 +389,7 @@ void WebSocketsClient::disconnect(void) {
  */
 void WebSocketsClient::setAuthorization(const char * user, const char * password) {
     if(user && password) {
-        String auth = user;
+        std::string auth = user;
         auth += ":";
         auth += password;
         _client.base64Authorization = base64_encode((uint8_t *)auth.c_str(), auth.length());
@@ -565,13 +568,13 @@ void WebSocketsClient::handleClientData(void) {
     if(len > 0) {
         switch(_client.status) {
             case WSC_HEADER: {
-                String headerLine = _client.tcp->readStringUntil('\n');
+                std::string headerLine = _client.tcp->readStringUntil('\n');
                 handleHeader(&_client, &headerLine);
             } break;
             case WSC_BODY: {
                 char buf[256] = { 0 };
                 _client.tcp->readBytes(&buf[0], std::min((size_t)len, sizeof(buf)));
-                String bodyLine = buf;
+                std::string bodyLine = buf;
                 handleHeader(&_client, &bodyLine);
             } break;
             case WSC_CONNECTED:
@@ -607,9 +610,9 @@ void WebSocketsClient::sendHeader(WSclient_t * client) {
     unsigned long start = micros();
 #endif
 
-    String handshake;
+    std::string handshake;
     bool ws_header = true;
-    String url     = client->cUrl;
+    std::string url     = client->cUrl;
 
     if(client->isSocketIO) {
         if(client->cSessionId.length() == 0) {
@@ -682,13 +685,13 @@ void WebSocketsClient::sendHeader(WSclient_t * client) {
  * handle the WebSocket header reading
  * @param client WSclient_t *  ptr to the client struct
  */
-void WebSocketsClient::handleHeader(WSclient_t * client, String * headerLine) {
+void WebSocketsClient::handleHeader(WSclient_t * client, std::string * headerLine) {
     headerLine->trim();    // remove \r
 
     // this code handels the http body for Socket.IO V3 requests
     if(headerLine->length() > 0 && client->isSocketIO && client->status == WSC_BODY && client->cSessionId.length() == 0) {
         DEBUG_WEBSOCKETS("[WS-Client][handleHeader] socket.io json: %s\n", headerLine->c_str());
-        String sid_begin = WEBSOCKETS_STRING("\"sid\":\"");
+        std::string sid_begin = WEBSOCKETS_STRING("\"sid\":\"");
         if(headerLine->indexOf(sid_begin) > -1) {
             int start          = headerLine->indexOf(sid_begin) + sid_begin.length();
             int end            = headerLine->indexOf('"', start);
@@ -708,8 +711,8 @@ void WebSocketsClient::handleHeader(WSclient_t * client, String * headerLine) {
             // "HTTP/1.1 101 Switching Protocols"
             client->cCode = headerLine->substring(9, headerLine->indexOf(' ', 9)).toInt();
         } else if(headerLine->indexOf(':') >= 0) {
-            String headerName  = headerLine->substring(0, headerLine->indexOf(':'));
-            String headerValue = headerLine->substring(headerLine->indexOf(':') + 1);
+            std::string headerName  = headerLine->substring(0, headerLine->indexOf(':'));
+            std::string headerValue = headerLine->substring(headerLine->indexOf(':') + 1);
 
             // remove space in the beginning  (RFC2616)
             if(headerValue[0] == ' ') {
@@ -800,7 +803,7 @@ void WebSocketsClient::handleHeader(WSclient_t * client, String * headerLine) {
                 ok = false;
             } else {
                 // generate Sec-WebSocket-Accept key for check
-                String sKey = acceptKey(client->cKey);
+                std::string sKey = acceptKey(client->cKey);
                 if(sKey != client->cAccept) {
                     DEBUG_WEBSOCKETS("[WS-Client][handleHeader] Sec-WebSocket-Accept is wrong\n");
                     ok = false;
diff --git a/src/WebSocketsClient.h b/src/WebSocketsClient.h
index efa7631..d1b7827 100644
--- a/src/WebSocketsClient.h
+++ b/src/WebSocketsClient.h
@@ -25,6 +25,8 @@
 #ifndef WEBSOCKETSCLIENT_H_
 #define WEBSOCKETSCLIENT_H_
 
+#include <string>
+
 #include "WebSockets.h"
 
 class WebSocketsClient : protected WebSockets {
@@ -39,13 +41,13 @@ class WebSocketsClient : protected WebSockets {
     virtual ~WebSocketsClient(void);
 
     void begin(const char * host, uint16_t port, const char * url = "/", const char * protocol = "arduino");
-    void begin(String host, uint16_t port, String url = "/", String protocol = "arduino");
+    void begin(std::string host, uint16_t port, std::string url = "/", std::string protocol = "arduino");
     void begin(IPAddress host, uint16_t port, const char * url = "/", const char * protocol = "arduino");
 
 #if defined(HAS_SSL)
 #ifdef SSL_AXTLS
     void beginSSL(const char * host, uint16_t port, const char * url = "/", const char * fingerprint = "", const char * protocol = "arduino");
-    void beginSSL(String host, uint16_t port, String url = "/", String fingerprint = "", String protocol = "arduino");
+    void beginSSL(std::string host, uint16_t port, std::string url = "/", std::string fingerprint = "", std::string protocol = "arduino");
 #else
     void beginSSL(const char * host, uint16_t port, const char * url = "/", const uint8_t * fingerprint = NULL, const char * protocol = "arduino");
     void beginSslWithCA(const char * host, uint16_t port, const char * url = "/", BearSSL::X509List * CA_cert = NULL, const char * protocol = "arduino");
@@ -56,11 +58,11 @@ class WebSocketsClient : protected WebSockets {
 #endif
 
     void beginSocketIO(const char * host, uint16_t port, const char * url = "/socket.io/?EIO=3", const char * protocol = "arduino");
-    void beginSocketIO(String host, uint16_t port, String url = "/socket.io/?EIO=3", String protocol = "arduino");
+    void beginSocketIO(std::string host, uint16_t port, std::string url = "/socket.io/?EIO=3", std::string protocol = "arduino");
 
 #if defined(HAS_SSL)
     void beginSocketIOSSL(const char * host, uint16_t port, const char * url = "/socket.io/?EIO=3", const char * protocol = "arduino");
-    void beginSocketIOSSL(String host, uint16_t port, String url = "/socket.io/?EIO=3", String protocol = "arduino");
+    void beginSocketIOSSL(std::string host, uint16_t port, std::string url = "/socket.io/?EIO=3", std::string protocol = "arduino");
 
     void beginSocketIOSSLWithCA(const char * host, uint16_t port, const char * url = "/socket.io/?EIO=3", const char * CA_cert = NULL, const char * protocol = "arduino");
 #if defined(SSL_BARESSL)
@@ -81,14 +83,14 @@ class WebSocketsClient : protected WebSockets {
     bool sendTXT(const uint8_t * payload, size_t length = 0);
     bool sendTXT(char * payload, size_t length = 0, bool headerToPayload = false);
     bool sendTXT(const char * payload, size_t length = 0);
-    bool sendTXT(String & payload);
+    bool sendTXT(std::string & payload);
     bool sendTXT(char payload);
 
     bool sendBIN(uint8_t * payload, size_t length, bool headerToPayload = false);
     bool sendBIN(const uint8_t * payload, size_t length);
 
     bool sendPing(uint8_t * payload = NULL, size_t length = 0);
-    bool sendPing(String & payload);
+    bool sendPing(std::string & payload);
 
     void disconnect(void);
 
@@ -105,12 +107,12 @@ class WebSocketsClient : protected WebSockets {
     bool isConnected(void);
 
   protected:
-    String _host;
+    std::string _host;
     uint16_t _port;
 
 #if defined(HAS_SSL)
 #ifdef SSL_AXTLS
-    String _fingerprint;
+    std::string _fingerprint;
     const char * _CA_cert;
 #define SSL_FINGERPRINT_IS_SET (_fingerprint.length())
 #define SSL_FINGERPRINT_NULL ""
@@ -142,7 +144,7 @@ class WebSocketsClient : protected WebSockets {
 #endif
 
     void sendHeader(WSclient_t * client);
-    void handleHeader(WSclient_t * client, String * headerLine);
+    void handleHeader(WSclient_t * client, std::string * headerLine);
 
     void connectedCb();
     void connectFailedCb();
diff --git a/src/WebSocketsServer.cpp b/src/WebSocketsServer.cpp
index 495cb55..a9eea51 100644
--- a/src/WebSocketsServer.cpp
+++ b/src/WebSocketsServer.cpp
@@ -22,10 +22,13 @@
  *
  */
 
-#include "WebSockets.h"
 #include "WebSocketsServer.h"
 
-WebSocketsServerCore::WebSocketsServerCore(const String & origin, const String & protocol) {
+#include <string>
+
+#include "WebSockets.h"
+
+WebSocketsServerCore::WebSocketsServerCore(const std::string & origin, const std::string & protocol) {
     _origin                 = origin;
     _protocol               = protocol;
     _runnning               = false;
@@ -40,7 +43,7 @@ WebSocketsServerCore::WebSocketsServerCore(const String & origin, const String &
     _mandatoryHttpHeaderCount = 0;
 }
 
-WebSocketsServer::WebSocketsServer(uint16_t port, const String & origin, const String & protocol)
+WebSocketsServer::WebSocketsServer(uint16_t port, const std::string & origin, const std::string & protocol)
     : WebSocketsServerCore(origin, protocol) {
     _port = port;
 
@@ -130,7 +133,7 @@ void WebSocketsServerCore::onValidateHttpHeader(
         delete[] _mandatoryHttpHeaders;
 
     _mandatoryHttpHeaderCount = mandatoryHttpHeaderCount;
-    _mandatoryHttpHeaders     = new String[_mandatoryHttpHeaderCount];
+    _mandatoryHttpHeaders     = new std::string[_mandatoryHttpHeaderCount];
 
     for(size_t i = 0; i < _mandatoryHttpHeaderCount; i++) {
         _mandatoryHttpHeaders[i] = mandatoryHttpHeaders[i];
@@ -171,7 +174,7 @@ bool WebSocketsServerCore::sendTXT(uint8_t num, const char * payload, size_t len
     return sendTXT(num, (uint8_t *)payload, length);
 }
 
-bool WebSocketsServerCore::sendTXT(uint8_t num, String & payload) {
+bool WebSocketsServerCore::sendTXT(uint8_t num, std::string & payload) {
     return sendTXT(num, (uint8_t *)payload.c_str(), payload.length());
 }
 
@@ -213,7 +216,7 @@ bool WebSocketsServerCore::broadcastTXT(const char * payload, size_t length) {
     return broadcastTXT((uint8_t *)payload, length);
 }
 
-bool WebSocketsServerCore::broadcastTXT(String & payload) {
+bool WebSocketsServerCore::broadcastTXT(std::string & payload) {
     return broadcastTXT((uint8_t *)payload.c_str(), payload.length());
 }
 
@@ -284,7 +287,7 @@ bool WebSocketsServerCore::sendPing(uint8_t num, uint8_t * payload, size_t lengt
     return false;
 }
 
-bool WebSocketsServerCore::sendPing(uint8_t num, String & payload) {
+bool WebSocketsServerCore::sendPing(uint8_t num, std::string & payload) {
     return sendPing(num, (uint8_t *)payload.c_str(), payload.length());
 }
 
@@ -309,7 +312,7 @@ bool WebSocketsServerCore::broadcastPing(uint8_t * payload, size_t length) {
     return ret;
 }
 
-bool WebSocketsServerCore::broadcastPing(String & payload) {
+bool WebSocketsServerCore::broadcastPing(std::string & payload) {
     return broadcastPing((uint8_t *)payload.c_str(), payload.length());
 }
 
@@ -347,7 +350,7 @@ void WebSocketsServerCore::disconnect(uint8_t num) {
  */
 void WebSocketsServerCore::setAuthorization(const char * user, const char * password) {
     if(user && password) {
-        String auth = user;
+        std::string auth = user;
         auth += ":";
         auth += password;
         _base64Authorization = base64_encode((uint8_t *)auth.c_str(), auth.length());
@@ -662,7 +665,7 @@ void WebSocketsServerCore::handleClientData(void) {
                 //DEBUG_WEBSOCKETS("[WS-Server][%d][handleClientData] len: %d\n", client->num, len);
                 switch(client->status) {
                     case WSC_HEADER: {
-                        String headerLine = client->tcp->readStringUntil('\n');
+                        std::string headerLine = client->tcp->readStringUntil('\n');
                         handleHeader(client, &headerLine);
                     } break;
                     case WSC_CONNECTED:
@@ -685,9 +688,9 @@ void WebSocketsServerCore::handleClientData(void) {
 
 /*
  * returns an indicator whether the given named header exists in the configured _mandatoryHttpHeaders collection
- * @param headerName String ///< the name of the header being checked
+ * @param headerName std::string ///< the name of the header being checked
  */
-bool WebSocketsServerCore::hasMandatoryHeader(String headerName) {
+bool WebSocketsServerCore::hasMandatoryHeader(std::string headerName) {
     for(size_t i = 0; i < _mandatoryHttpHeaderCount; i++) {
         if(_mandatoryHttpHeaders[i].equalsIgnoreCase(headerName))
             return true;
@@ -698,9 +701,9 @@ bool WebSocketsServerCore::hasMandatoryHeader(String headerName) {
 /**
  * handles http header reading for WebSocket upgrade
  * @param client WSclient_t * ///< pointer to the client struct
- * @param headerLine String ///< the header being read / processed
+ * @param headerLine std::string ///< the header being read / processed
  */
-void WebSocketsServerCore::handleHeader(WSclient_t * client, String * headerLine) {
+void WebSocketsServerCore::handleHeader(WSclient_t * client, std::string * headerLine) {
     static const char * NEW_LINE = "\r\n";
 
     headerLine->trim();    // remove \r
@@ -718,8 +721,8 @@ void WebSocketsServerCore::handleHeader(WSclient_t * client, String * headerLine
             client->cMandatoryHeadersCount = 0;
 
         } else if(headerLine->indexOf(':') >= 0) {
-            String headerName  = headerLine->substring(0, headerLine->indexOf(':'));
-            String headerValue = headerLine->substring(headerLine->indexOf(':') + 1);
+            std::string headerName  = headerLine->substring(0, headerLine->indexOf(':'));
+            std::string headerValue = headerLine->substring(headerLine->indexOf(':') + 1);
 
             // remove space in the beginning (RFC2616)
             if(headerValue[0] == ' ') {
@@ -795,7 +798,7 @@ void WebSocketsServerCore::handleHeader(WSclient_t * client, String * headerLine
         }
 
         if(_base64Authorization.length() > 0) {
-            String auth = WEBSOCKETS_STRING("Basic ");
+            std::string auth = WEBSOCKETS_STRING("Basic ");
             auth += _base64Authorization;
             if(auth != client->base64Authorization) {
                 DEBUG_WEBSOCKETS("[WS-Server][%d][handleHeader] HTTP Authorization failed!\n", client->num);
@@ -808,13 +811,13 @@ void WebSocketsServerCore::handleHeader(WSclient_t * client, String * headerLine
             DEBUG_WEBSOCKETS("[WS-Server][%d][handleHeader] Websocket connection incoming.\n", client->num);
 
             // generate Sec-WebSocket-Accept key
-            String sKey = acceptKey(client->cKey);
+            std::string sKey = acceptKey(client->cKey);
 
             DEBUG_WEBSOCKETS("[WS-Server][%d][handleHeader]  - sKey: %s\n", client->num, sKey.c_str());
 
             client->status = WSC_CONNECTED;
 
-            String handshake = WEBSOCKETS_STRING(
+            std::string handshake = WEBSOCKETS_STRING(
                 "HTTP/1.1 101 Switching Protocols\r\n"
                 "Server: arduino-WebSocketsServer\r\n"
                 "Upgrade: websocket\r\n"
diff --git a/src/WebSocketsServer.h b/src/WebSocketsServer.h
index 5bdcd04..538b7a4 100644
--- a/src/WebSocketsServer.h
+++ b/src/WebSocketsServer.h
@@ -25,6 +25,8 @@
 #ifndef WEBSOCKETSSERVER_H_
 #define WEBSOCKETSSERVER_H_
 
+#include <string>
+
 #include "WebSockets.h"
 
 #ifndef WEBSOCKETS_SERVER_CLIENT_MAX
@@ -33,7 +35,7 @@
 
 class WebSocketsServerCore : protected WebSockets {
   public:
-    WebSocketsServerCore(const String & origin = "", const String & protocol = "arduino");
+    WebSocketsServerCore(const std::string & origin = "", const std::string & protocol = "arduino");
     virtual ~WebSocketsServerCore(void);
 
     void begin(void);
@@ -41,10 +43,10 @@ class WebSocketsServerCore : protected WebSockets {
 
 #ifdef __AVR__
     typedef void (*WebSocketServerEvent)(uint8_t num, WStype_t type, uint8_t * payload, size_t length);
-    typedef bool (*WebSocketServerHttpHeaderValFunc)(String headerName, String headerValue);
+    typedef bool (*WebSocketServerHttpHeaderValFunc)(std::string headerName, std::string headerValue);
 #else
     typedef std::function<void(uint8_t num, WStype_t type, uint8_t * payload, size_t length)> WebSocketServerEvent;
-    typedef std::function<bool(String headerName, String headerValue)> WebSocketServerHttpHeaderValFunc;
+    typedef std::function<bool(std::string headerName, std::string headerValue)> WebSocketServerHttpHeaderValFunc;
 #endif
 
     void onEvent(WebSocketServerEvent cbEvent);
@@ -57,13 +59,13 @@ class WebSocketsServerCore : protected WebSockets {
     bool sendTXT(uint8_t num, const uint8_t * payload, size_t length = 0);
     bool sendTXT(uint8_t num, char * payload, size_t length = 0, bool headerToPayload = false);
     bool sendTXT(uint8_t num, const char * payload, size_t length = 0);
-    bool sendTXT(uint8_t num, String & payload);
+    bool sendTXT(uint8_t num, std::string & payload);
 
     bool broadcastTXT(uint8_t * payload, size_t length = 0, bool headerToPayload = false);
     bool broadcastTXT(const uint8_t * payload, size_t length = 0);
     bool broadcastTXT(char * payload, size_t length = 0, bool headerToPayload = false);
     bool broadcastTXT(const char * payload, size_t length = 0);
-    bool broadcastTXT(String & payload);
+    bool broadcastTXT(std::string & payload);
 
     bool sendBIN(uint8_t num, uint8_t * payload, size_t length, bool headerToPayload = false);
     bool sendBIN(uint8_t num, const uint8_t * payload, size_t length);
@@ -72,10 +74,10 @@ class WebSocketsServerCore : protected WebSockets {
     bool broadcastBIN(const uint8_t * payload, size_t length);
 
     bool sendPing(uint8_t num, uint8_t * payload = NULL, size_t length = 0);
-    bool sendPing(uint8_t num, String & payload);
+    bool sendPing(uint8_t num, std::string & payload);
 
     bool broadcastPing(uint8_t * payload = NULL, size_t length = 0);
-    bool broadcastPing(String & payload);
+    bool broadcastPing(std::string & payload);
 
     void disconnect(void);
     void disconnect(uint8_t num);
@@ -101,10 +103,10 @@ class WebSocketsServerCore : protected WebSockets {
     WSclient_t * newClient(WEBSOCKETS_NETWORK_CLASS * TCPclient);
 
   protected:
-    String _origin;
-    String _protocol;
-    String _base64Authorization;    ///< Base64 encoded Auth request
-    String * _mandatoryHttpHeaders;
+    std::string _origin;
+    std::string _protocol;
+    std::string _base64Authorization;    ///< Base64 encoded Auth request
+    std::string * _mandatoryHttpHeaders;
     size_t _mandatoryHttpHeaderCount;
 
     WSclient_t _clients[WEBSOCKETS_SERVER_CLIENT_MAX];
@@ -127,7 +129,7 @@ class WebSocketsServerCore : protected WebSockets {
     void handleClientData(void);
 #endif
 
-    void handleHeader(WSclient_t * client, String * headerLine);
+    void handleHeader(WSclient_t * client, std::string * headerLine);
 
     void handleHBPing(WSclient_t * client);    // send ping in specified intervals
 
@@ -190,7 +192,7 @@ class WebSocketsServerCore : protected WebSockets {
          * This mechanism can be used to enable custom authentication schemes e.g. test the value
          * of a session cookie to determine if a user is logged on / authenticated
          */
-    virtual bool execHttpHeaderValidation(String headerName, String headerValue) {
+    virtual bool execHttpHeaderValidation(std::string headerName, std::string headerValue) {
         if(_httpHeaderValidationFunc) {
             //return the value of the custom http header validation function
             return _httpHeaderValidationFunc(headerName, headerValue);
@@ -211,14 +213,14 @@ class WebSocketsServerCore : protected WebSockets {
   private:
     /*
          * returns an indicator whether the given named header exists in the configured _mandatoryHttpHeaders collection
-         * @param headerName String ///< the name of the header being checked
+         * @param headerName std::string ///< the name of the header being checked
          */
-    bool hasMandatoryHeader(String headerName);
+    bool hasMandatoryHeader(std::string headerName);
 };
 
 class WebSocketsServer : public WebSocketsServerCore {
   public:
-    WebSocketsServer(uint16_t port, const String & origin = "", const String & protocol = "arduino");
+    WebSocketsServer(uint16_t port, const std::string & origin = "", const std::string & protocol = "arduino");
     virtual ~WebSocketsServer(void);
 
     void begin(void);