diff --git a/include/tcp.h b/include/tcp.h
index aad83b0..748a4bc 100644
--- a/include/tcp.h
+++ b/include/tcp.h
@@ -117,7 +117,7 @@ namespace Tins {
         void dport(uint16_t new_dport);
         
         /** \brief Set the source port.
-         * \param new_dport New source port.
+         * \param new_sport New source port.
          */
         void sport(uint16_t new_sport);
         
@@ -151,6 +151,7 @@ namespace Tins {
          * Payload is NOT copied. Therefore, pointers provided as 
          * payloads must be freed manually by the user.
          * \param new_payload New payload.
+         * \param new_payload_size New payload's size
          */
         void payload(uint8_t *new_payload, uint32_t new_payload_size);
         
diff --git a/include/udp.h b/include/udp.h
new file mode 100644
index 0000000..6918029
--- /dev/null
+++ b/include/udp.h
@@ -0,0 +1,46 @@
+#ifndef __UDP_H
+#define __UDP_H
+
+
+#include "pdu.h"
+
+namespace Tins {
+
+    /** \brief UDP represents the UDP PDU.
+     * 
+     * UDP is the representation of the UDP PDU. Instances of this class
+     * must be sent over a level 3 PDU, this will otherwise fail.
+     */
+    class UDP : public PDU {
+    public:
+        /** \brief UDP constructor.
+         * 
+         * Creates an instance of UDP. Destination and source port can
+         * be provided, otherwise both will be 0.
+         * \param dport Destination port.
+         * \param sport Source port.
+         * */
+        UDP(uint16_t sport = 0, uint16_t dport = 0);
+        
+        /** \brief Set the payload.
+         * 
+         * Payload is NOT copied. Therefore, pointers provided as 
+         * payloads must be freed manually by the user.
+         * \param new_payload New payload.
+         * \param new_payload_size New payload's size
+         */
+        void payload(uint8_t *new_payload, uint32_t new_payload_size);
+    private:
+        struct udphdr {
+            uint16_t sport;
+            uint16_t dport;
+            uint16_t len;
+            uint16_t check;
+        } __attribute__((packed));
+        
+        udphdr _udp;
+        uint8_t *payload;
+    };
+};
+
+#endif
diff --git a/src/ip.cpp b/src/ip.cpp
index 9aecd3b..d4cf501 100644
--- a/src/ip.cpp
+++ b/src/ip.cpp
@@ -126,8 +126,6 @@ void Tins::IP::set_option(uint8_t copied,
     option.type.number = number;
     uint8_t* buffer(0);
     if (data_size) {
-        /* data must be a valid pointer */
-        assert(data);
         buffer = new uint8_t[data_size];
         memcpy(buffer, data, data_size);
     }
diff --git a/src/tcp.cpp b/src/tcp.cpp
index a50713d..8b7bba3 100644
--- a/src/tcp.cpp
+++ b/src/tcp.cpp
@@ -37,6 +37,7 @@ Tins::TCP::TCP(uint16_t dport, uint16_t sport) : PDU(IPPROTO_TCP), _payload(0),
     _tcp.sport = Utils::net_to_host_s(sport);
     _tcp.doff = sizeof(tcphdr) / sizeof(uint32_t);
     _tcp.window = Utils::net_to_host_s(DEFAULT_WINDOW);
+    _tcp.check = 0;
 }
 
 Tins::TCP::~TCP() {
@@ -153,7 +154,8 @@ void Tins::TCP::write_serialization(uint8_t *buffer, uint32_t total_sz) {
     }
         
     memcpy(buffer, _payload, _payload_size);
-    _tcp.check = Utils::net_to_host_s(do_checksum(tcp_start + sizeof(tcphdr), buffer));
+    if(!_tcp.check)
+        _tcp.check = Utils::net_to_host_s(do_checksum(tcp_start + sizeof(tcphdr), buffer));
     memcpy(tcp_start, &_tcp, sizeof(tcphdr));
 }
 
diff --git a/src/udp.cpp b/src/udp.cpp
new file mode 100644
index 0000000..e634811
--- /dev/null
+++ b/src/udp.cpp
@@ -0,0 +1,14 @@
+#ifndef WIN32
+    #include <netinet/in.h>
+#endif
+#include "udp.h"
+
+Tins::UDP::UDP(uint16_t sport, uint16_t dport) : PDU(IPPROTO_UDP), _payload(0) {
+    _udp.sport = sport;
+    _udp.dport = dport;
+}
+
+void Tins::UDP::payload(uint8_t *new_payload, uint32_t new_payload_size) {
+    _payload = new_payload;
+    _udp.len = sizeof(udphdr) + new_payload_size;
+}