diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4030255..f6d6c01 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -46,6 +46,7 @@ add_executable(${TARGET_NAME})
 # lwip
 set (LWIP_INCLUDE_DIRS
     "${LWIP_DIR}/src/include"
+    "${LWIP_DIR}/src/include/compat/posix"
     "bsp_z7/lwip/include"
     #${LWIP_DIR}/contrib/ports/freertos/include
 )
diff --git a/bsp_z7/hardware/uart.c b/bsp_z7/hardware/uart.c
index bfec1f1..ddfe8a6 100644
--- a/bsp_z7/hardware/uart.c
+++ b/bsp_z7/hardware/uart.c
@@ -77,6 +77,7 @@ void uart0_enable_receiver() {
 }
 
 int uart0_read(char *ptr, int len) {
+  // TODO for blocking, if first call was successfull, further calls need to be delay=0
   int received = 0;
   while (len > 0) {
     BaseType_t result = xQueueReceive(uart0_receive_queue, ptr, 0);
diff --git a/bsp_z7/lwip/include/lwipopts.h b/bsp_z7/lwip/include/lwipopts.h
index 4c6d126..a3b8132 100644
--- a/bsp_z7/lwip/include/lwipopts.h
+++ b/bsp_z7/lwip/include/lwipopts.h
@@ -36,9 +36,9 @@
 #define LWIP_IPV6                  0
 
 #define NO_SYS                     0
-#define LWIP_SOCKET                (NO_SYS==0)
-#define LWIP_NETCONN               (NO_SYS==0)
-#define LWIP_NETIF_API             (NO_SYS==0)
+#define LWIP_SOCKET                1
+#define LWIP_NETCONN               1
+#define LWIP_NETIF_API             0
 
 #define LWIP_IGMP                  0
 #define LWIP_ICMP                  LWIP_IPV4
@@ -60,9 +60,17 @@
 
 #define TCP_LISTEN_BACKLOG         0
 
-#define LWIP_COMPAT_SOCKETS        0
-#define LWIP_SO_RCVTIMEO           0
-#define LWIP_SO_RCVBUF             0
+#define LWIP_COMPAT_SOCKETS         2
+//TODO put this into the OS
+#define LWIP_POSIX_SOCKETS_IO_NAMES 0
+#define LWIP_SO_RCVTIMEO            0
+#define LWIP_SO_RCVBUF              0
+//TODO use this with LWIP_POSIX_SOCKETS_IO_NAMES
+// TODO why is 100 not working...
+#define LWIP_SOCKET_OFFSET          10
+
+#define LWIP_SOCKET_SELECT          1
+#define LWIP_SOCKET_POLL            1
 
 #define LWIP_TCPIP_CORE_LOCKING    0
 
diff --git a/bsp_z7/testEth.c b/bsp_z7/testEth.c
index 62fc939..cdb8c0e 100644
--- a/bsp_z7/testEth.c
+++ b/bsp_z7/testEth.c
@@ -1,12 +1,134 @@
+#include "lwip/api.h"
+#include "lwip/priv/sockets_priv.h"
 #include "lwip/tcpip.h"
+
+#include "sys/socket.h"
+
 #include "FreeRTOS.h"
 #include "task.h"
 
-
 #include "xethernet.h"
 
-int testEth(){
+#include "hardware/interfaces.h"
+#include <unistd.h>
+
+struct lwip_sock *get_socket(int fd);
+
+extern QueueHandle_t uart0_receive_queue;
+
+void udp_echo_thread(void *_) {
+  vTaskDelay(5000 * portTICK_RATE_MS);
+
+  int sock = socket(AF_INET, SOCK_DGRAM, 0);
+  if (sock == -1) {
+    xil_printf("no sock\n");
+  }
+
+  struct sockaddr_in our_addr;
+  memset(&our_addr, 0, sizeof(our_addr));
+
+  our_addr.sin_family = AF_INET;
+  our_addr.sin_port = htons(8100);
+
+  int ret = inet_aton("192.168.1.10", &our_addr.sin_addr);
+  if (ret == 0) {
+    xil_printf("no addr");
+  }
+
+  ret = bind(sock, (struct sockaddr *)&our_addr, sizeof(our_addr));
+  if (ret == -1) {
+    xil_printf("no bind");
+  }
+
+  struct sockaddr_in peer_addr;
+  memset(&peer_addr, 0, sizeof(peer_addr));
+
+  peer_addr.sin_family = AF_INET;
+  peer_addr.sin_port = htons(8100);
+
+  ret = inet_aton("192.168.1.5", &peer_addr.sin_addr);
+  if (ret == 0) {
+    xil_printf("no addr");
+  }
+
+  int uart_sock = hw_device_open("uart0", 5);
+  write(uart_sock, "1234", 4);
+
+  // char buffer[] = {'1','2','3','4'};
+  // ret = sendto(sock, buffer, sizeof(buffer), 0, (struct sockaddr *)
+  // &peer_addr, sizeof(peer_addr)); if (ret <= 0) {
+  //   xil_printf("no send");
+  // }
+
+  uint8_t rec_buffer[1024];
+
+  QueueSetHandle_t listening_set = xQueueCreateSet(100);
+  if (listening_set == NULL) {
+    xil_printf("no set");
+  }
+
+  struct lwip_sock *raw_socket = get_socket(sock);
+
+  sys_mbox_t queue_id = raw_socket->conn->recvmbox;
+
+  xQueueAddToSet(queue_id, listening_set);
+  xQueueAddToSet(uart0_receive_queue, listening_set);
+
+  while (1) {
+    QueueSetMemberHandle_t readable =
+        xQueueSelectFromSet(listening_set, portMAX_DELAY);
+
+    if (readable == queue_id) {
+      socklen_t peer_len = sizeof(peer_addr);
+      ret = lwip_recvfrom(sock, rec_buffer, sizeof(rec_buffer), 0, (struct sockaddr *) &peer_addr,
+                     &peer_len);
+      if (peer_len > sizeof(peer_addr)) {
+        xil_printf("invalid peer");
+        continue;
+      }
+      if (ret < 0) {
+        continue;
+      }
+      uint16_t port = ntohs(peer_addr.sin_port);
+      switch (port) {
+      case 8100:
+        xil_printf("udp rec 8100 len: %i\n", ret);
+        write(uart_sock, rec_buffer, ret);
+        break;
+      default:
+        xil_printf("invalid port %i\n", port);
+        break;
+      }
+    } else if (readable == uart0_receive_queue) {
+      ret = read(uart_sock, rec_buffer, sizeof(rec_buffer));
+      xil_printf("uart got %i\n", ret);
+
+      // Do not send empty packets
+      if (ret <= 0) {
+        continue;
+      }
+      peer_addr.sin_port = htons(8100);
+
+      //TODO sending 1 byte gives invalid UDP checksum
+      lwip_sendto(sock, rec_buffer, ret, 0, (struct sockaddr *)&peer_addr,
+             sizeof(peer_addr));
+    } else {
+      xil_printf("invalid handle");
+    }
+  }
+
+  xQueueRemoveFromSet(queue_id, listening_set);
+
+  while (1) {
+    ret = recv(sock, rec_buffer, sizeof(rec_buffer), 0);
+    xil_printf("received %i\n", ret);
+    vTaskDelay(100 * portTICK_RATE_MS);
+  }
+}
+
+int testEth() {
   tcpip_init(NULL, NULL);
   xethernet_init();
-	vTaskStartScheduler();
+  sys_thread_new("echo", udp_echo_thread, 0, 1024, DEFAULT_THREAD_PRIO);
+  vTaskStartScheduler();
 }
\ No newline at end of file