diff --git a/src/coap.cpp b/src/coap.cpp
new file mode 100644
index 0000000..b1d49a4
--- /dev/null
+++ b/src/coap.cpp
@@ -0,0 +1,124 @@
+#include "coap.h"
+
+namespace coap {
+
+uint8_t CoapMessage::getVersion() {
+    return vertkl >> 6;
+}
+
+uint8_t CoapMessage::getType() {
+    return (vertkl & 0x30) >> 4;
+}
+
+uint8_t CoapMessage::getTKL() {
+    return (vertkl & 0x0f);
+}
+
+uint8_t CoapMessage::getCode() {
+    return code;
+}
+
+const char* CoapMessage::getMID() {
+    return id;
+}
+
+/* nonsense: save 8 bits in the network,
+   and waste tens of them for writing such an error-prone code like this! */
+int CoapMessage::getOptionDelta(const unsigned char* option) {
+    uint8_t delta = option[0] >> 4;
+    if (delta <= 12) {
+        return delta;
+    }
+
+    if (delta == 13) {
+        delta = option[1] + 13;
+        return delta;
+    }
+
+    /* options delta larger than 269 (256 + 13) bytes are not supported */
+    return -1;
+}
+int CoapMessage::getOptionLength(const unsigned char* option) {
+    uint8_t len = option[0] & 0xf;
+
+    if (len <= 12) {
+        return len;
+    }
+
+    uint8_t extended_length_byte;
+    if (getOptionDelta(option) < 13)
+        extended_length_byte = option[1];
+    else
+        extended_length_byte = option[2];
+
+    if (len == 13) {
+        len = extended_length_byte + 13;
+        return len;
+    }
+
+    /* options longer than 269 (256 + 13) are not supported */
+    return -1;
+}
+/* offset of payload wrt beginning of option */
+int CoapMessage::getOptionValueOffset(const unsigned char* option) {
+    int offset = 1;
+    if (getOptionDelta(option) >= 13) ++offset;
+    if (getOptionLength(option) >= 13) ++offset;
+    return offset;
+}
+const char* CoapMessage::getOptionValue(const unsigned char* option) {
+    return (const char*) &option[getOptionValueOffset(option)];
+}
+const unsigned char* CoapMessage::getOptions() {
+    const unsigned char* address = (const unsigned char*)this;
+    address += 4;  /* header */
+    address += getTKL();
+    return address;
+}
+
+void CoapMessage::getUriPath(char* output_buffer, const char* last) {
+    /* TODO -- possible overflow, malformed input not checked */
+    int number = 0;
+    int len;
+    const unsigned char* options = this->getOptions();
+
+    while (number <= 11) {
+        number += getOptionDelta(options);
+        len = getOptionLength(options);
+        // TODO -- is here a payload? 15 - 15
+        if (number == 11) { /* Uri-Path option number */
+            *output_buffer = '/';
+            output_buffer += 1;
+            memcpy(output_buffer, getOptionValue(options), len);
+            output_buffer += len;
+        }
+        options += (len + getOptionValueOffset(options));
+        if (options == last) break;
+    }
+
+    *output_buffer = '\0';
+
+    return;
+}
+
+int coap_server(char* output_buffer, const char* input_buffer, int len) {
+    CoapMessage* input_msg = (CoapMessage*) input_buffer;
+    if (input_msg->getVersion() != 0x1) /* bad CoAP version number */
+        return -1;
+
+    if (input_msg->getType() == RESET || input_msg->getType() == ACKNOWELEDGMENT) /* not implemented on server side */
+        return -1;
+
+    if (input_msg->getTKL() >= 9)   /* format error -- TODO, maybe we can answer RST? see RFC */
+        return -1;
+
+    switch (input_msg->getCode()) {
+        case GET:
+            input_msg->getUriPath(output_buffer, input_buffer + len);
+            return strlen(output_buffer);
+            break;
+    }
+    return -1;
+}
+
+} // end of namespace -- coap::
diff --git a/src/coap.h b/src/coap.h
new file mode 100644
index 0000000..ad7ae20
--- /dev/null
+++ b/src/coap.h
@@ -0,0 +1,53 @@
+#ifndef COAP_H
+#define COAP_H
+
+#include "Arduino.h"
+
+namespace coap {
+
+    enum Type {
+        CONFIRMABLE = 0,
+        NON_CONFIRMABLE = 1,
+        ACKNOWELEDGMENT = 2,
+        RESET = 3
+    };
+    enum Code {
+        EMPTY = 0x00,   /* 0.00 */
+        GET = 0x01,     /* 0.01 */
+        POST = 0x02,    /* 0.02 */
+        PUT = 0x03,     /* 0.03 */
+        DELETE = 0x04,  /* 0.04 */
+        CONTENT = 0x45, /* 2.05 */
+        NOT_FOUND = 0x84,/*4.04 */
+        METHOD_NOT_ALLOWED = 0x85   /* 4.05 */
+    };
+
+    class CoapMessage {
+        private:
+            char vertkl;
+            char code;
+            char id[2];
+        public:
+            uint8_t getVersion();
+            uint8_t getType();
+            uint8_t getTKL();
+            uint8_t getCode();
+            const char* getMID();
+            const char* getPayload();
+
+            int getOptionDelta(const unsigned char* option);
+            int getOptionLength(const unsigned char* option);
+            const char* getOptionValue(const unsigned char* option);
+            int getOptionValueOffset(const unsigned char* option);
+            const unsigned char* getOptions();
+
+            void getUriPath(char* output_buffer, const char* last);
+
+
+    };
+
+    int coap_server(char* output_buffer, const char* input_buffer, int len);
+
+}
+
+#endif
\ No newline at end of file