diff --git a/compiler/options.nim b/compiler/options.nim
index 8ff8cb753a1f..56b0613586a4 100644
--- a/compiler/options.nim
+++ b/compiler/options.nim
@@ -494,7 +494,7 @@ proc isDefined*(conf: ConfigRef; symbol: string): bool =
                             osQnx, osAtari, osAix,
                             osHaiku, osVxWorks, osSolaris, osNetbsd,
                             osFreebsd, osOpenbsd, osDragonfly, osMacosx, osIos,
-                            osAndroid, osNintendoSwitch}
+                            osAndroid, osNintendoSwitch, osFreeRTOS}
     of "linux":
       result = conf.target.targetOS in {osLinux, osAndroid}
     of "bsd":
@@ -510,6 +510,10 @@ proc isDefined*(conf: ConfigRef; symbol: string): bool =
     of "sunos": result = conf.target.targetOS == osSolaris
     of "nintendoswitch":
       result = conf.target.targetOS == osNintendoSwitch
+    of "freertos":
+      result = conf.target.targetOS == osFreeRTOS
+    of "lwip":
+      result = conf.target.targetOS in {osFreeRTOS}
     of "littleendian": result = CPU[conf.target.targetCPU].endian == platform.littleEndian
     of "bigendian": result = CPU[conf.target.targetCPU].endian == platform.bigEndian
     of "cpu8": result = CPU[conf.target.targetCPU].bit == 8
diff --git a/compiler/platform.nim b/compiler/platform.nim
index 4bac7c5a15e5..df79b2f8dc14 100644
--- a/compiler/platform.nim
+++ b/compiler/platform.nim
@@ -22,7 +22,7 @@ type
     osNone, osDos, osWindows, osOs2, osLinux, osMorphos, osSkyos, osSolaris,
     osIrix, osNetbsd, osFreebsd, osOpenbsd, osDragonfly, osAix, osPalmos, osQnx,
     osAmiga, osAtari, osNetware, osMacos, osMacosx, osIos, osHaiku, osAndroid, osVxWorks
-    osGenode, osJS, osNimVM, osStandalone, osNintendoSwitch, osAny
+    osGenode, osJS, osNimVM, osStandalone, osNintendoSwitch, osFreeRTOS, osAny
 
 type
   TInfoOSProp* = enum
@@ -177,6 +177,10 @@ const
       objExt: ".o", newLine: "\x0A", pathSep: ":", dirSep: "/",
       scriptExt: ".sh", curDir: ".", exeExt: ".elf", extSep: ".",
       props: {ospNeedsPIC, ospPosix}),
+     (name: "FreeRTOS", parDir: "..", dllFrmt: "lib$1.so", altDirSep: "/",
+      objExt: ".o", newLine: "\x0A", pathSep: ":", dirSep: "/",
+      scriptExt: ".sh", curDir: ".", exeExt: ".elf", extSep: ".",
+      props: {ospPosix}),
      (name: "Any", parDir: "..", dllFrmt: "lib$1.so", altDirSep: "/",
       objExt: ".o", newLine: "\x0A", pathSep: ":", dirSep: "/",
       scriptExt: ".sh", curDir: ".", exeExt: "", extSep: ".",
@@ -189,7 +193,7 @@ type
     cpuNone, cpuI386, cpuM68k, cpuAlpha, cpuPowerpc, cpuPowerpc64,
     cpuPowerpc64el, cpuSparc, cpuVm, cpuHppa, cpuIa64, cpuAmd64, cpuMips,
     cpuMipsel, cpuArm, cpuArm64, cpuJS, cpuNimVM, cpuAVR, cpuMSP430,
-    cpuSparc64, cpuMips64, cpuMips64el, cpuRiscV64, cpuWasm32
+    cpuSparc64, cpuMips64, cpuMips64el, cpuRiscV64, cpuEsp, cpuWasm32
 
 type
   TEndian* = enum
@@ -223,6 +227,7 @@ const
     (name: "mips64", intSize: 64, endian: bigEndian, floatSize: 64, bit: 64),
     (name: "mips64el", intSize: 64, endian: littleEndian, floatSize: 64, bit: 64),
     (name: "riscv64", intSize: 64, endian: littleEndian, floatSize: 64, bit: 64),
+    (name: "esp", intSize: 32, endian: littleEndian, floatSize: 64, bit: 32),
     (name: "wasm32", intSize: 32, endian: littleEndian, floatSize: 64, bit: 32)]
 
 type
diff --git a/lib/posix/posix.nim b/lib/posix/posix.nim
index d3d9728abfed..c7a324cde4f1 100644
--- a/lib/posix/posix.nim
+++ b/lib/posix/posix.nim
@@ -962,9 +962,15 @@ proc IN6_IS_ADDR_LINKLOCAL* (a1: ptr In6Addr): cint {.
 proc IN6_IS_ADDR_SITELOCAL* (a1: ptr In6Addr): cint {.
   importc, header: "<netinet/in.h>".}
   ## Unicast site-local address.
-proc IN6_IS_ADDR_V4MAPPED* (a1: ptr In6Addr): cint {.
-  importc, header: "<netinet/in.h>".}
-  ## IPv4 mapped address.
+when defined(lwip):
+  proc IN6_IS_ADDR_V4MAPPED*(ipv6_address: ptr In6Addr): cint =
+    var bits32: ptr array[4, uint32] = cast[ptr array[4, uint32]](ipv6_address)
+    return (bits32[1] == 0'u32 and bits32[2] == htonl(0x0000FFFF)).cint
+else:
+  proc IN6_IS_ADDR_V4MAPPED* (a1: ptr In6Addr): cint {.
+    importc, header: "<netinet/in.h>".}
+    ## IPv4 mapped address.
+
 proc IN6_IS_ADDR_V4COMPAT* (a1: ptr In6Addr): cint {.
   importc, header: "<netinet/in.h>".}
   ## IPv4-compatible address.
@@ -1026,8 +1032,9 @@ proc setnetent*(a1: cint) {.importc, header: "<netdb.h>".}
 proc setprotoent*(a1: cint) {.importc, header: "<netdb.h>".}
 proc setservent*(a1: cint) {.importc, header: "<netdb.h>".}
 
-proc poll*(a1: ptr TPollfd, a2: Tnfds, a3: int): cint {.
-  importc, header: "<poll.h>", sideEffect.}
+when not defined(lwip):
+  proc poll*(a1: ptr TPollfd, a2: Tnfds, a3: int): cint {.
+    importc, header: "<poll.h>", sideEffect.}
 
 proc realpath*(name, resolved: cstring): cstring {.
   importc: "realpath", header: "<stdlib.h>".}
diff --git a/lib/posix/posix_freertos_consts.nim b/lib/posix/posix_freertos_consts.nim
new file mode 100644
index 000000000000..5e83fa0f5e78
--- /dev/null
+++ b/lib/posix/posix_freertos_consts.nim
@@ -0,0 +1,488 @@
+# Generated by detect.nim
+
+
+
+# <errno.h>
+var E2BIG* {.importc: "E2BIG", header: "<errno.h>".}: cint
+var EACCES* {.importc: "EACCES", header: "<errno.h>".}: cint
+var EADDRINUSE* {.importc: "EADDRINUSE", header: "<errno.h>".}: cint
+var EADDRNOTAVAIL* {.importc: "EADDRNOTAVAIL", header: "<errno.h>".}: cint
+var EAFNOSUPPORT* {.importc: "EAFNOSUPPORT", header: "<errno.h>".}: cint
+var EAGAIN* {.importc: "EAGAIN", header: "<errno.h>".}: cint
+var EALREADY* {.importc: "EALREADY", header: "<errno.h>".}: cint
+var EBADF* {.importc: "EBADF", header: "<errno.h>".}: cint
+var EBADMSG* {.importc: "EBADMSG", header: "<errno.h>".}: cint
+var EBUSY* {.importc: "EBUSY", header: "<errno.h>".}: cint
+var ECANCELED* {.importc: "ECANCELED", header: "<errno.h>".}: cint
+var ECHILD* {.importc: "ECHILD", header: "<errno.h>".}: cint
+var ECONNABORTED* {.importc: "ECONNABORTED", header: "<errno.h>".}: cint
+var ECONNREFUSED* {.importc: "ECONNREFUSED", header: "<errno.h>".}: cint
+var ECONNRESET* {.importc: "ECONNRESET", header: "<errno.h>".}: cint
+var EDEADLK* {.importc: "EDEADLK", header: "<errno.h>".}: cint
+var EDESTADDRREQ* {.importc: "EDESTADDRREQ", header: "<errno.h>".}: cint
+var EDOM* {.importc: "EDOM", header: "<errno.h>".}: cint
+var EDQUOT* {.importc: "EDQUOT", header: "<errno.h>".}: cint
+var EEXIST* {.importc: "EEXIST", header: "<errno.h>".}: cint
+var EFAULT* {.importc: "EFAULT", header: "<errno.h>".}: cint
+var EFBIG* {.importc: "EFBIG", header: "<errno.h>".}: cint
+var EHOSTUNREACH* {.importc: "EHOSTUNREACH", header: "<errno.h>".}: cint
+var EIDRM* {.importc: "EIDRM", header: "<errno.h>".}: cint
+var EILSEQ* {.importc: "EILSEQ", header: "<errno.h>".}: cint
+var EINPROGRESS* {.importc: "EINPROGRESS", header: "<errno.h>".}: cint
+var EINTR* {.importc: "EINTR", header: "<errno.h>".}: cint
+var EINVAL* {.importc: "EINVAL", header: "<errno.h>".}: cint
+var EIO* {.importc: "EIO", header: "<errno.h>".}: cint
+var EISCONN* {.importc: "EISCONN", header: "<errno.h>".}: cint
+var EISDIR* {.importc: "EISDIR", header: "<errno.h>".}: cint
+var ELOOP* {.importc: "ELOOP", header: "<errno.h>".}: cint
+var EMFILE* {.importc: "EMFILE", header: "<errno.h>".}: cint
+var EMLINK* {.importc: "EMLINK", header: "<errno.h>".}: cint
+var EMSGSIZE* {.importc: "EMSGSIZE", header: "<errno.h>".}: cint
+var EMULTIHOP* {.importc: "EMULTIHOP", header: "<errno.h>".}: cint
+var ENAMETOOLONG* {.importc: "ENAMETOOLONG", header: "<errno.h>".}: cint
+var ENETDOWN* {.importc: "ENETDOWN", header: "<errno.h>".}: cint
+var ENETRESET* {.importc: "ENETRESET", header: "<errno.h>".}: cint
+var ENETUNREACH* {.importc: "ENETUNREACH", header: "<errno.h>".}: cint
+var ENFILE* {.importc: "ENFILE", header: "<errno.h>".}: cint
+var ENOBUFS* {.importc: "ENOBUFS", header: "<errno.h>".}: cint
+var ENODATA* {.importc: "ENODATA", header: "<errno.h>".}: cint
+var ENODEV* {.importc: "ENODEV", header: "<errno.h>".}: cint
+var ENOENT* {.importc: "ENOENT", header: "<errno.h>".}: cint
+var ENOEXEC* {.importc: "ENOEXEC", header: "<errno.h>".}: cint
+var ENOLCK* {.importc: "ENOLCK", header: "<errno.h>".}: cint
+var ENOLINK* {.importc: "ENOLINK", header: "<errno.h>".}: cint
+var ENOMEM* {.importc: "ENOMEM", header: "<errno.h>".}: cint
+var ENOMSG* {.importc: "ENOMSG", header: "<errno.h>".}: cint
+var ENOPROTOOPT* {.importc: "ENOPROTOOPT", header: "<errno.h>".}: cint
+var ENOSPC* {.importc: "ENOSPC", header: "<errno.h>".}: cint
+var ENOSR* {.importc: "ENOSR", header: "<errno.h>".}: cint
+var ENOSTR* {.importc: "ENOSTR", header: "<errno.h>".}: cint
+var ENOSYS* {.importc: "ENOSYS", header: "<errno.h>".}: cint
+var ENOTCONN* {.importc: "ENOTCONN", header: "<errno.h>".}: cint
+var ENOTDIR* {.importc: "ENOTDIR", header: "<errno.h>".}: cint
+var ENOTEMPTY* {.importc: "ENOTEMPTY", header: "<errno.h>".}: cint
+var ENOTSOCK* {.importc: "ENOTSOCK", header: "<errno.h>".}: cint
+var ENOTSUP* {.importc: "ENOTSUP", header: "<errno.h>".}: cint
+var ENOTTY* {.importc: "ENOTTY", header: "<errno.h>".}: cint
+var ENXIO* {.importc: "ENXIO", header: "<errno.h>".}: cint
+var EOPNOTSUPP* {.importc: "EOPNOTSUPP", header: "<errno.h>".}: cint
+var EOVERFLOW* {.importc: "EOVERFLOW", header: "<errno.h>".}: cint
+var EPERM* {.importc: "EPERM", header: "<errno.h>".}: cint
+var EPIPE* {.importc: "EPIPE", header: "<errno.h>".}: cint
+var EPROTO* {.importc: "EPROTO", header: "<errno.h>".}: cint
+var EPROTONOSUPPORT* {.importc: "EPROTONOSUPPORT", header: "<errno.h>".}: cint
+var EPROTOTYPE* {.importc: "EPROTOTYPE", header: "<errno.h>".}: cint
+var ERANGE* {.importc: "ERANGE", header: "<errno.h>".}: cint
+var EROFS* {.importc: "EROFS", header: "<errno.h>".}: cint
+var ESPIPE* {.importc: "ESPIPE", header: "<errno.h>".}: cint
+var ESRCH* {.importc: "ESRCH", header: "<errno.h>".}: cint
+var ESTALE* {.importc: "ESTALE", header: "<errno.h>".}: cint
+var ETIME* {.importc: "ETIME", header: "<errno.h>".}: cint
+var ETIMEDOUT* {.importc: "ETIMEDOUT", header: "<errno.h>".}: cint
+var ETXTBSY* {.importc: "ETXTBSY", header: "<errno.h>".}: cint
+var EWOULDBLOCK* {.importc: "EWOULDBLOCK", header: "<errno.h>".}: cint
+var EXDEV* {.importc: "EXDEV", header: "<errno.h>".}: cint
+
+# <sys/fcntl.h>
+var F_GETFD* {.importc: "F_GETFD", header: "<sys/fcntl.h>".}: cint
+# var F_SETFD* {.importc: "F_SETFD", header: "<sys/fcntl.h>".}: cint
+var F_GETFL* {.importc: "F_GETFL", header: "<sys/fcntl.h>".}: cint
+var F_SETFL* {.importc: "F_SETFL", header: "<sys/fcntl.h>".}: cint
+# var F_GETLK* {.importc: "F_GETLK", header: "<sys/fcntl.h>".}: cint
+# var F_SETLK* {.importc: "F_SETLK", header: "<sys/fcntl.h>".}: cint
+# var F_SETLKW* {.importc: "F_SETLKW", header: "<sys/fcntl.h>".}: cint
+# var F_GETOWN* {.importc: "F_GETOWN", header: "<sys/fcntl.h>".}: cint
+# var F_SETOWN* {.importc: "F_SETOWN", header: "<sys/fcntl.h>".}: cint
+# var FD_CLOEXEC* {.importc: "FD_CLOEXEC", header: "<sys/fcntl.h>".}: cint
+# var F_RDLCK* {.importc: "F_RDLCK", header: "<sys/fcntl.h>".}: cint
+# var F_UNLCK* {.importc: "F_UNLCK", header: "<sys/fcntl.h>".}: cint
+# var F_WRLCK* {.importc: "F_WRLCK", header: "<sys/fcntl.h>".}: cint
+var O_CREAT* {.importc: "O_CREAT", header: "<sys/fcntl.h>".}: cint
+var O_EXCL* {.importc: "O_EXCL", header: "<sys/fcntl.h>".}: cint
+# var O_NOCTTY* {.importc: "O_NOCTTY", header: "<sys/fcntl.h>".}: cint
+var O_TRUNC* {.importc: "O_TRUNC", header: "<sys/fcntl.h>".}: cint
+var O_APPEND* {.importc: "O_APPEND", header: "<sys/fcntl.h>".}: cint
+# var O_DSYNC* {.importc: "O_DSYNC", header: "<sys/fcntl.h>".}: cint
+var O_NONBLOCK* {.importc: "O_NONBLOCK", header: "<sys/fcntl.h>".}: cint
+# var O_RSYNC* {.importc: "O_RSYNC", header: "<sys/fcntl.h>".}: cint
+# var O_SYNC* {.importc: "O_SYNC", header: "<sys/fcntl.h>".}: cint
+# var O_ACCMODE* {.importc: "O_ACCMODE", header: "<sys/fcntl.h>".}: cint
+var O_RDONLY* {.importc: "O_RDONLY", header: "<sys/fcntl.h>".}: cint
+var O_RDWR* {.importc: "O_RDWR", header: "<sys/fcntl.h>".}: cint
+var O_WRONLY* {.importc: "O_WRONLY", header: "<sys/fcntl.h>".}: cint
+# var O_CLOEXEC* {.importc: "O_CLOEXEC", header: "<sys/fcntl.h>".}: cint
+
+# # <locale.h>
+# var LC_ALL* {.importc: "LC_ALL", header: "<locale.h>".}: cint
+# var LC_COLLATE* {.importc: "LC_COLLATE", header: "<locale.h>".}: cint
+# var LC_CTYPE* {.importc: "LC_CTYPE", header: "<locale.h>".}: cint
+# var LC_MESSAGES* {.importc: "LC_MESSAGES", header: "<locale.h>".}: cint
+# var LC_MONETARY* {.importc: "LC_MONETARY", header: "<locale.h>".}: cint
+# var LC_NUMERIC* {.importc: "LC_NUMERIC", header: "<locale.h>".}: cint
+# var LC_TIME* {.importc: "LC_TIME", header: "<locale.h>".}: cint
+
+# <netdb.h>
+var HOST_NOT_FOUND* {.importc: "HOST_NOT_FOUND", header: "<netdb.h>".}: cint
+var NO_DATA* {.importc: "NO_DATA", header: "<netdb.h>".}: cint
+var NO_RECOVERY* {.importc: "NO_RECOVERY", header: "<netdb.h>".}: cint
+var TRY_AGAIN* {.importc: "TRY_AGAIN", header: "<netdb.h>".}: cint
+var AI_PASSIVE* {.importc: "AI_PASSIVE", header: "<netdb.h>".}: cint
+var AI_CANONNAME* {.importc: "AI_CANONNAME", header: "<netdb.h>".}: cint
+var AI_NUMERICHOST* {.importc: "AI_NUMERICHOST", header: "<netdb.h>".}: cint
+var AI_NUMERICSERV* {.importc: "AI_NUMERICSERV", header: "<netdb.h>".}: cint
+var AI_V4MAPPED* {.importc: "AI_V4MAPPED", header: "<netdb.h>".}: cint
+var AI_ALL* {.importc: "AI_ALL", header: "<netdb.h>".}: cint
+var AI_ADDRCONFIG* {.importc: "AI_ADDRCONFIG", header: "<netdb.h>".}: cint
+var NI_NOFQDN* {.importc: "NI_NOFQDN", header: "<netdb.h>".}: cint
+var NI_NUMERICHOST* {.importc: "NI_NUMERICHOST", header: "<netdb.h>".}: cint
+var NI_NAMEREQD* {.importc: "NI_NAMEREQD", header: "<netdb.h>".}: cint
+var NI_NUMERICSERV* {.importc: "NI_NUMERICSERV", header: "<netdb.h>".}: cint
+var NI_DGRAM* {.importc: "NI_DGRAM", header: "<netdb.h>".}: cint
+var EAI_AGAIN* {.importc: "EAI_AGAIN", header: "<netdb.h>".}: cint
+var EAI_BADFLAGS* {.importc: "EAI_BADFLAGS", header: "<netdb.h>".}: cint
+var EAI_FAIL* {.importc: "EAI_FAIL", header: "<netdb.h>".}: cint
+var EAI_FAMILY* {.importc: "EAI_FAMILY", header: "<netdb.h>".}: cint
+var EAI_MEMORY* {.importc: "EAI_MEMORY", header: "<netdb.h>".}: cint
+var EAI_NONAME* {.importc: "EAI_NONAME", header: "<netdb.h>".}: cint
+var EAI_SERVICE* {.importc: "EAI_SERVICE", header: "<netdb.h>".}: cint
+var EAI_SOCKTYPE* {.importc: "EAI_SOCKTYPE", header: "<netdb.h>".}: cint
+
+var LWIP_DNS_API_DECLARE_H_ERRNO* {.importc: "LWIP_DNS_API_DECLARE_H_ERRNO", header: "<netdb.h>".}: cint
+var LWIP_DNS_API_DEFINE_ERRORS* {.importc: "LWIP_DNS_API_DEFINE_ERRORS", header: "<netdb.h>".}: cint
+var LWIP_DNS_API_DEFINE_FLAGS* {.importc: "LWIP_DNS_API_DEFINE_FLAGS", header: "<netdb.h>".}: cint
+var LWIP_DNS_API_DECLARE_STRUCTS* {.importc: "LWIP_DNS_API_DECLARE_STRUCTS", header: "<netdb.h>".}: cint
+var NETDB_ELEM_SIZE* {.importc: "NETDB_ELEM_SIZE", header: "<netdb.h>".}: cint
+
+
+# <netif.h>
+var ENABLE_LOOPBACK* {.importc: "ENABLE_LOOPBACK", header: "<netif.h>".}: cint
+var NETIF_MAX_HWADDR_LEN* {.importc: "NETIF_MAX_HWADDR_LEN", header: "<netif.h>".}: cint
+var NETIF_NAMESIZE* {.importc: "NETIF_NAMESIZE", header: "<netif.h>".}: cint
+var NETIF_FLAG_UP* {.importc: "NETIF_FLAG_UP", header: "<netif.h>".}: cint
+var NETIF_FLAG_BROADCAST* {.importc: "NETIF_FLAG_BROADCAST", header: "<netif.h>".}: cint
+var NETIF_FLAG_LINK_UP* {.importc: "NETIF_FLAG_LINK_UP", header: "<netif.h>".}: cint
+var NETIF_FLAG_ETHARP* {.importc: "NETIF_FLAG_ETHARP", header: "<netif.h>".}: cint
+var NETIF_FLAG_ETHERNET* {.importc: "NETIF_FLAG_ETHERNET", header: "<netif.h>".}: cint
+var NETIF_FLAG_IGMP* {.importc: "NETIF_FLAG_IGMP", header: "<netif.h>".}: cint
+var NETIF_FLAG_MLD6* {.importc: "NETIF_FLAG_MLD6", header: "<netif.h>".}: cint
+var NETIF_FLAG_GARP* {.importc: "NETIF_FLAG_GARP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_GEN_IP* {.importc: "NETIF_CHECKSUM_GEN_IP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_GEN_UDP* {.importc: "NETIF_CHECKSUM_GEN_UDP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_GEN_TCP* {.importc: "NETIF_CHECKSUM_GEN_TCP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_GEN_ICMP* {.importc: "NETIF_CHECKSUM_GEN_ICMP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_GEN_ICMP6* {.importc: "NETIF_CHECKSUM_GEN_ICMP6", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_CHECK_IP* {.importc: "NETIF_CHECKSUM_CHECK_IP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_CHECK_UDP* {.importc: "NETIF_CHECKSUM_CHECK_UDP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_CHECK_TCP* {.importc: "NETIF_CHECKSUM_CHECK_TCP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_CHECK_ICMP* {.importc: "NETIF_CHECKSUM_CHECK_ICMP", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_CHECK_ICMP6* {.importc: "NETIF_CHECKSUM_CHECK_ICMP6", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_ENABLE_ALL* {.importc: "NETIF_CHECKSUM_ENABLE_ALL", header: "<netif.h>".}: cint
+var NETIF_CHECKSUM_DISABLE_ALL* {.importc: "NETIF_CHECKSUM_DISABLE_ALL", header: "<netif.h>".}: cint
+var NETIF_ADDR_IDX_MAX* {.importc: "NETIF_ADDR_IDX_MAX", header: "<netif.h>".}: cint
+var LWIP_NETIF_USE_HINTS* {.importc: "LWIP_NETIF_USE_HINTS", header: "<netif.h>".}: cint
+var NETIF_NO_INDEX* {.importc: "NETIF_NO_INDEX", header: "<netif.h>".}: cint
+var LWIP_NSC_NONE* {.importc: "LWIP_NSC_NONE", header: "<netif.h>".}: cint
+var LWIP_NSC_NETIF_ADDED* {.importc: "LWIP_NSC_NETIF_ADDED", header: "<netif.h>".}: cint
+var LWIP_NSC_NETIF_REMOVED* {.importc: "LWIP_NSC_NETIF_REMOVED", header: "<netif.h>".}: cint
+var LWIP_NSC_LINK_CHANGED* {.importc: "LWIP_NSC_LINK_CHANGED", header: "<netif.h>".}: cint
+var LWIP_NSC_STATUS_CHANGED* {.importc: "LWIP_NSC_STATUS_CHANGED", header: "<netif.h>".}: cint
+var LWIP_NSC_IPV4_ADDRESS_CHANGED* {.importc: "LWIP_NSC_IPV4_ADDRESS_CHANGED", header: "<netif.h>".}: cint
+var LWIP_NSC_IPV4_GATEWAY_CHANGED* {.importc: "LWIP_NSC_IPV4_GATEWAY_CHANGED", header: "<netif.h>".}: cint
+var LWIP_NSC_IPV4_NETMASK_CHANGED* {.importc: "LWIP_NSC_IPV4_NETMASK_CHANGED", header: "<netif.h>".}: cint
+var LWIP_NSC_IPV4_SETTINGS_CHANGED* {.importc: "LWIP_NSC_IPV4_SETTINGS_CHANGED", header: "<netif.h>".}: cint
+var LWIP_NSC_IPV6_SET* {.importc: "LWIP_NSC_IPV6_SET", header: "<netif.h>".}: cint
+var LWIP_NSC_IPV6_ADDR_STATE_CHANGED* {.importc: "LWIP_NSC_IPV6_ADDR_STATE_CHANGED", header: "<netif.h>".}: cint
+#define NETIF_DECLARE_EXT_CALLBACK(name)
+
+
+# <net/if.h>
+var IF_NAMESIZE* {.importc: "IF_NAMESIZE", header: "<net/if.h>".}: cint
+
+# <sys/socket.h>
+var IPPROTO_IP* {.importc: "IPPROTO_IP", header: "<sys/socket.h>".}: cint
+var IPPROTO_IPV6* {.importc: "IPPROTO_IPV6", header: "<sys/socket.h>".}: cint
+var IPPROTO_ICMP* {.importc: "IPPROTO_ICMP", header: "<sys/socket.h>".}: cint
+var IPPROTO_ICMPV6* {.importc: "IPPROTO_ICMPV6", header: "<sys/socket.h>".}: cint
+var IPPROTO_RAW* {.importc: "IPPROTO_RAW", header: "<sys/socket.h>".}: cint
+var IPPROTO_TCP* {.importc: "IPPROTO_TCP", header: "<sys/socket.h>".}: cint
+var IPPROTO_UDP* {.importc: "IPPROTO_UDP", header: "<sys/socket.h>".}: cint
+var INADDR_ANY* {.importc: "INADDR_ANY", header: "<sys/socket.h>".}: InAddrScalar
+var INADDR_LOOPBACK* {.importc: "INADDR_LOOPBACK", header: "<sys/socket.h>".}: InAddrScalar
+var INADDR_BROADCAST* {.importc: "INADDR_BROADCAST", header: "<sys/socket.h>".}: InAddrScalar
+var INET_ADDRSTRLEN* {.importc: "INET_ADDRSTRLEN", header: "<sys/socket.h>".}: cint
+var INET6_ADDRSTRLEN* {.importc: "INET6_ADDRSTRLEN", header: "<sys/socket.h>".}: cint
+var IPV6_JOIN_GROUP* {.importc: "IPV6_JOIN_GROUP", header: "<sys/socket.h>".}: cint
+var IPV6_LEAVE_GROUP* {.importc: "IPV6_LEAVE_GROUP", header: "<sys/socket.h>".}: cint
+var IPV6_MULTICAST_HOPS* {.importc: "IPV6_MULTICAST_HOPS", header: "<sys/socket.h>".}: cint
+var IPV6_MULTICAST_IF* {.importc: "IPV6_MULTICAST_IF", header: "<sys/socket.h>".}: cint
+var IPV6_MULTICAST_LOOP* {.importc: "IPV6_MULTICAST_LOOP", header: "<sys/socket.h>".}: cint
+var IPV6_UNICAST_HOPS* {.importc: "IPV6_UNICAST_HOPS", header: "<sys/socket.h>".}: cint
+var IPV6_V6ONLY* {.importc: "IPV6_V6ONLY", header: "<sys/socket.h>".}: cint
+
+# <netinet/tcp.h>
+var TCP_NODELAY* {.importc: "TCP_NODELAY", header: "<sys/socket.h>".}: cint
+var TCP_KEEPALIVE* {.importc: "TCP_KEEPALIVE", header: "<sys/socket.h>".}: cint
+var TCP_KEEPIDLE* {.importc: "TCP_KEEPIDLE", header: "<sys/socket.h>".}: cint
+var TCP_KEEPINTVL* {.importc: "TCP_KEEPINTVL", header: "<sys/socket.h>".}: cint
+var TCP_KEEPCNT* {.importc: "TCP_KEEPCNT", header: "<sys/socket.h>".}: cint
+
+# <nl_types.h>
+# var NL_SETD* {.importc: "NL_SETD", header: "<nl_types.h>".}: cint
+# var NL_CAT_LOCALE* {.importc: "NL_CAT_LOCALE", header: "<nl_types.h>".}: cint
+
+# <sys/poll.h>
+# var POLLIN* {.importc: "POLLIN", header: "<sys/poll.h>".}: cshort
+# var POLLRDNORM* {.importc: "POLLRDNORM", header: "<sys/poll.h>".}: cshort
+# var POLLRDBAND* {.importc: "POLLRDBAND", header: "<sys/poll.h>".}: cshort
+# var POLLPRI* {.importc: "POLLPRI", header: "<sys/poll.h>".}: cshort
+# var POLLOUT* {.importc: "POLLOUT", header: "<sys/poll.h>".}: cshort
+# var POLLWRNORM* {.importc: "POLLWRNORM", header: "<sys/poll.h>".}: cshort
+# var POLLWRBAND* {.importc: "POLLWRBAND", header: "<sys/poll.h>".}: cshort
+# var POLLERR* {.importc: "POLLERR", header: "<sys/poll.h>".}: cshort
+# var POLLHUP* {.importc: "POLLHUP", header: "<sys/poll.h>".}: cshort
+# var POLLNVAL* {.importc: "POLLNVAL", header: "<sys/poll.h>".}: cshort
+
+# <pthread.h>
+var PTHREAD_STACK_MIN* {.importc: "PTHREAD_STACK_MIN", header: "<pthread.h>".}: cint
+# var PTHREAD_BARRIER_SERIAL_THREAD* {.importc: "PTHREAD_BARRIER_SERIAL_THREAD", header: "<pthread.h>".}: cint
+# var PTHREAD_CANCEL_ASYNCHRONOUS* {.importc: "PTHREAD_CANCEL_ASYNCHRONOUS", header: "<pthread.h>".}: cint
+# var PTHREAD_CANCEL_ENABLE* {.importc: "PTHREAD_CANCEL_ENABLE", header: "<pthread.h>".}: cint
+# var PTHREAD_CANCEL_DEFERRED* {.importc: "PTHREAD_CANCEL_DEFERRED", header: "<pthread.h>".}: cint
+# var PTHREAD_CANCEL_DISABLE* {.importc: "PTHREAD_CANCEL_DISABLE", header: "<pthread.h>".}: cint
+# var PTHREAD_CREATE_DETACHED* {.importc: "PTHREAD_CREATE_DETACHED", header: "<pthread.h>".}: cint
+# var PTHREAD_CREATE_JOINABLE* {.importc: "PTHREAD_CREATE_JOINABLE", header: "<pthread.h>".}: cint
+# var PTHREAD_EXPLICIT_SCHED* {.importc: "PTHREAD_EXPLICIT_SCHED", header: "<pthread.h>".}: cint
+# var PTHREAD_INHERIT_SCHED* {.importc: "PTHREAD_INHERIT_SCHED", header: "<pthread.h>".}: cint
+# var PTHREAD_MUTEX_DEFAULT* {.importc: "PTHREAD_MUTEX_DEFAULT", header: "<pthread.h>".}: cint
+# var PTHREAD_MUTEX_ERRORCHECK* {.importc: "PTHREAD_MUTEX_ERRORCHECK", header: "<pthread.h>".}: cint
+# var PTHREAD_MUTEX_NORMAL* {.importc: "PTHREAD_MUTEX_NORMAL", header: "<pthread.h>".}: cint
+# var PTHREAD_MUTEX_RECURSIVE* {.importc: "PTHREAD_MUTEX_RECURSIVE", header: "<pthread.h>".}: cint
+# var PTHREAD_PRIO_INHERIT* {.importc: "PTHREAD_PRIO_INHERIT", header: "<pthread.h>".}: cint
+# var PTHREAD_PRIO_NONE* {.importc: "PTHREAD_PRIO_NONE", header: "<pthread.h>".}: cint
+# var PTHREAD_PRIO_PROTECT* {.importc: "PTHREAD_PRIO_PROTECT", header: "<pthread.h>".}: cint
+# var PTHREAD_PROCESS_SHARED* {.importc: "PTHREAD_PROCESS_SHARED", header: "<pthread.h>".}: cint
+# var PTHREAD_PROCESS_PRIVATE* {.importc: "PTHREAD_PROCESS_PRIVATE", header: "<pthread.h>".}: cint
+# var PTHREAD_SCOPE_PROCESS* {.importc: "PTHREAD_SCOPE_PROCESS", header: "<pthread.h>".}: cint
+# var PTHREAD_SCOPE_SYSTEM* {.importc: "PTHREAD_SCOPE_SYSTEM", header: "<pthread.h>".}: cint
+
+# # <sched.h>
+# var SCHED_FIFO* {.importc: "SCHED_FIFO", header: "<sched.h>".}: cint
+# var SCHED_RR* {.importc: "SCHED_RR", header: "<sched.h>".}: cint
+# var SCHED_SPORADIC* {.importc: "SCHED_SPORADIC", header: "<sched.h>".}: cint
+# var SCHED_OTHER* {.importc: "SCHED_OTHER", header: "<sched.h>".}: cint
+
+# <semaphore.h>
+var SEM_FAILED* {.importc: "SEM_FAILED", header: "<semaphore.h>".}: pointer
+
+# # <signal.h>
+# var SIGEV_NONE* {.importc: "SIGEV_NONE", header: "<signal.h>".}: cint
+# var SIGEV_SIGNAL* {.importc: "SIGEV_SIGNAL", header: "<signal.h>".}: cint
+# var SIGEV_THREAD* {.importc: "SIGEV_THREAD", header: "<signal.h>".}: cint
+# var SIGABRT* {.importc: "SIGABRT", header: "<signal.h>".}: cint
+# var SIGALRM* {.importc: "SIGALRM", header: "<signal.h>".}: cint
+# var SIGBUS* {.importc: "SIGBUS", header: "<signal.h>".}: cint
+# var SIGCHLD* {.importc: "SIGCHLD", header: "<signal.h>".}: cint
+# var SIGCONT* {.importc: "SIGCONT", header: "<signal.h>".}: cint
+# var SIGFPE* {.importc: "SIGFPE", header: "<signal.h>".}: cint
+# var SIGHUP* {.importc: "SIGHUP", header: "<signal.h>".}: cint
+# var SIGILL* {.importc: "SIGILL", header: "<signal.h>".}: cint
+# var SIGINT* {.importc: "SIGINT", header: "<signal.h>".}: cint
+# var SIGKILL* {.importc: "SIGKILL", header: "<signal.h>".}: cint
+# var SIGPIPE* {.importc: "SIGPIPE", header: "<signal.h>".}: cint
+# var SIGQUIT* {.importc: "SIGQUIT", header: "<signal.h>".}: cint
+# var SIGSEGV* {.importc: "SIGSEGV", header: "<signal.h>".}: cint
+# var SIGSTOP* {.importc: "SIGSTOP", header: "<signal.h>".}: cint
+# var SIGTERM* {.importc: "SIGTERM", header: "<signal.h>".}: cint
+# var SIGTSTP* {.importc: "SIGTSTP", header: "<signal.h>".}: cint
+# var SIGTTIN* {.importc: "SIGTTIN", header: "<signal.h>".}: cint
+# var SIGTTOU* {.importc: "SIGTTOU", header: "<signal.h>".}: cint
+# var SIGUSR1* {.importc: "SIGUSR1", header: "<signal.h>".}: cint
+# var SIGUSR2* {.importc: "SIGUSR2", header: "<signal.h>".}: cint
+# var SIGPOLL* {.importc: "SIGPOLL", header: "<signal.h>".}: cint
+# var SIGPROF* {.importc: "SIGPROF", header: "<signal.h>".}: cint
+# var SIGSYS* {.importc: "SIGSYS", header: "<signal.h>".}: cint
+# var SIGTRAP* {.importc: "SIGTRAP", header: "<signal.h>".}: cint
+# var SIGURG* {.importc: "SIGURG", header: "<signal.h>".}: cint
+# var SIGVTALRM* {.importc: "SIGVTALRM", header: "<signal.h>".}: cint
+# var SIGXCPU* {.importc: "SIGXCPU", header: "<signal.h>".}: cint
+# var SIGXFSZ* {.importc: "SIGXFSZ", header: "<signal.h>".}: cint
+# var SA_NOCLDSTOP* {.importc: "SA_NOCLDSTOP", header: "<signal.h>".}: cint
+# var SIG_BLOCK* {.importc: "SIG_BLOCK", header: "<signal.h>".}: cint
+# var SIG_UNBLOCK* {.importc: "SIG_UNBLOCK", header: "<signal.h>".}: cint
+# var SIG_SETMASK* {.importc: "SIG_SETMASK", header: "<signal.h>".}: cint
+# var SA_ONSTACK* {.importc: "SA_ONSTACK", header: "<signal.h>".}: cint
+# var SA_RESETHAND* {.importc: "SA_RESETHAND", header: "<signal.h>".}: cint
+# var SA_RESTART* {.importc: "SA_RESTART", header: "<signal.h>".}: cint
+# var SA_SIGINFO* {.importc: "SA_SIGINFO", header: "<signal.h>".}: cint
+# var SA_NOCLDWAIT* {.importc: "SA_NOCLDWAIT", header: "<signal.h>".}: cint
+# var SA_NODEFER* {.importc: "SA_NODEFER", header: "<signal.h>".}: cint
+# var SS_ONSTACK* {.importc: "SS_ONSTACK", header: "<signal.h>".}: cint
+# var SS_DISABLE* {.importc: "SS_DISABLE", header: "<signal.h>".}: cint
+# var MINSIGSTKSZ* {.importc: "MINSIGSTKSZ", header: "<signal.h>".}: cint
+# var SIGSTKSZ* {.importc: "SIGSTKSZ", header: "<signal.h>".}: cint
+# var SIG_HOLD* {.importc: "SIG_HOLD", header: "<signal.h>".}: Sighandler
+# var SIG_DFL* {.importc: "SIG_DFL", header: "<signal.h>".}: Sighandler
+# var SIG_ERR* {.importc: "SIG_ERR", header: "<signal.h>".}: Sighandler
+# var SIG_IGN* {.importc: "SIG_IGN", header: "<signal.h>".}: Sighandler
+
+# # <sys/ipc.h>
+# var IPC_CREAT* {.importc: "IPC_CREAT", header: "<sys/ipc.h>".}: cint
+# var IPC_EXCL* {.importc: "IPC_EXCL", header: "<sys/ipc.h>".}: cint
+# var IPC_NOWAIT* {.importc: "IPC_NOWAIT", header: "<sys/ipc.h>".}: cint
+# var IPC_PRIVATE* {.importc: "IPC_PRIVATE", header: "<sys/ipc.h>".}: cint
+# var IPC_RMID* {.importc: "IPC_RMID", header: "<sys/ipc.h>".}: cint
+# var IPC_SET* {.importc: "IPC_SET", header: "<sys/ipc.h>".}: cint
+# var IPC_STAT* {.importc: "IPC_STAT", header: "<sys/ipc.h>".}: cint
+
+# # <sys/mman.h>
+# var PROT_READ* {.importc: "PROT_READ", header: "<sys/mman.h>".}: cint
+# var PROT_WRITE* {.importc: "PROT_WRITE", header: "<sys/mman.h>".}: cint
+# var PROT_EXEC* {.importc: "PROT_EXEC", header: "<sys/mman.h>".}: cint
+# var PROT_NONE* {.importc: "PROT_NONE", header: "<sys/mman.h>".}: cint
+# var MAP_ANONYMOUS* {.importc: "MAP_ANONYMOUS", header: "<sys/mman.h>".}: cint
+# var MAP_FIXED_NOREPLACE* {.importc: "MAP_FIXED_NOREPLACE", header: "<sys/mman.h>".}: cint
+# var MAP_NORESERVE* {.importc: "MAP_NORESERVE", header: "<sys/mman.h>".}: cint
+# var MAP_SHARED* {.importc: "MAP_SHARED", header: "<sys/mman.h>".}: cint
+# var MAP_PRIVATE* {.importc: "MAP_PRIVATE", header: "<sys/mman.h>".}: cint
+# var MAP_FIXED* {.importc: "MAP_FIXED", header: "<sys/mman.h>".}: cint
+# var MS_ASYNC* {.importc: "MS_ASYNC", header: "<sys/mman.h>".}: cint
+# var MS_SYNC* {.importc: "MS_SYNC", header: "<sys/mman.h>".}: cint
+# var MS_INVALIDATE* {.importc: "MS_INVALIDATE", header: "<sys/mman.h>".}: cint
+# var MCL_CURRENT* {.importc: "MCL_CURRENT", header: "<sys/mman.h>".}: cint
+# var MCL_FUTURE* {.importc: "MCL_FUTURE", header: "<sys/mman.h>".}: cint
+# var MAP_FAILED* {.importc: "MAP_FAILED", header: "<sys/mman.h>".}: pointer
+# var POSIX_MADV_NORMAL* {.importc: "POSIX_MADV_NORMAL", header: "<sys/mman.h>".}: cint
+# var POSIX_MADV_SEQUENTIAL* {.importc: "POSIX_MADV_SEQUENTIAL", header: "<sys/mman.h>".}: cint
+# var POSIX_MADV_RANDOM* {.importc: "POSIX_MADV_RANDOM", header: "<sys/mman.h>".}: cint
+# var POSIX_MADV_WILLNEED* {.importc: "POSIX_MADV_WILLNEED", header: "<sys/mman.h>".}: cint
+# var POSIX_MADV_DONTNEED* {.importc: "POSIX_MADV_DONTNEED", header: "<sys/mman.h>".}: cint
+# var POSIX_TYPED_MEM_ALLOCATE* {.importc: "POSIX_TYPED_MEM_ALLOCATE", header: "<sys/mman.h>".}: cint
+# var POSIX_TYPED_MEM_ALLOCATE_CONTIG* {.importc: "POSIX_TYPED_MEM_ALLOCATE_CONTIG", header: "<sys/mman.h>".}: cint
+# var POSIX_TYPED_MEM_MAP_ALLOCATABLE* {.importc: "POSIX_TYPED_MEM_MAP_ALLOCATABLE", header: "<sys/mman.h>".}: cint
+
+# <sys/resource.h>
+# var RLIMIT_NOFILE* {.importc: "RLIMIT_NOFILE", header: "<sys/resource.h>".}: cint
+
+# <sys/select.h>
+var FD_SETSIZE* {.importc: "FD_SETSIZE", header: "<sys/select.h>".}: cint
+
+# <sys/socket.h>
+var MSG_CTRUNC* {.importc: "MSG_CTRUNC", header: "<sys/socket.h>".}: cint
+var MSG_DONTROUTE* {.importc: "MSG_DONTROUTE", header: "<sys/socket.h>".}: cint
+var MSG_EOR* {.importc: "MSG_EOR", header: "<sys/socket.h>".}: cint
+var MSG_OOB* {.importc: "MSG_OOB", header: "<sys/socket.h>".}: cint
+
+# var SCM_RIGHTS* {.importc: "SCM_RIGHTS", header: "<sys/socket.h>".}: cint
+var SO_ACCEPTCONN* {.importc: "SO_ACCEPTCONN", header: "<sys/socket.h>".}: cint
+var SO_BROADCAST* {.importc: "SO_BROADCAST", header: "<sys/socket.h>".}: cint
+var SO_DEBUG* {.importc: "SO_DEBUG", header: "<sys/socket.h>".}: cint
+var SO_DONTROUTE* {.importc: "SO_DONTROUTE", header: "<sys/socket.h>".}: cint
+var SO_ERROR* {.importc: "SO_ERROR", header: "<sys/socket.h>".}: cint
+var SO_KEEPALIVE* {.importc: "SO_KEEPALIVE", header: "<sys/socket.h>".}: cint
+var SO_LINGER* {.importc: "SO_LINGER", header: "<sys/socket.h>".}: cint
+var SO_OOBINLINE* {.importc: "SO_OOBINLINE", header: "<sys/socket.h>".}: cint
+var SO_RCVBUF* {.importc: "SO_RCVBUF", header: "<sys/socket.h>".}: cint
+var SO_RCVLOWAT* {.importc: "SO_RCVLOWAT", header: "<sys/socket.h>".}: cint
+var SO_RCVTIMEO* {.importc: "SO_RCVTIMEO", header: "<sys/socket.h>".}: cint
+var SO_REUSEADDR* {.importc: "SO_REUSEADDR", header: "<sys/socket.h>".}: cint
+var SO_SNDBUF* {.importc: "SO_SNDBUF", header: "<sys/socket.h>".}: cint
+var SO_SNDLOWAT* {.importc: "SO_SNDLOWAT", header: "<sys/socket.h>".}: cint
+var SO_SNDTIMEO* {.importc: "SO_SNDTIMEO", header: "<sys/socket.h>".}: cint
+var SO_TYPE* {.importc: "SO_TYPE", header: "<sys/socket.h>".}: cint
+var SOCK_DGRAM* {.importc: "SOCK_DGRAM", header: "<sys/socket.h>".}: cint
+var SOCK_RAW* {.importc: "SOCK_RAW", header: "<sys/socket.h>".}: cint
+
+# var SOCK_SEQPACKET* {.importc: "SOCK_SEQPACKET", header: "<sys/socket.h>".}: cint
+const SOCK_SEQPACKET* = cint(5)
+
+var SOCK_STREAM* {.importc: "SOCK_STREAM", header: "<sys/socket.h>".}: cint
+var SOL_SOCKET* {.importc: "SOL_SOCKET", header: "<sys/socket.h>".}: cint
+
+const SocketMaxConnections {.intdefine.}: int = 32
+var SOMAXCONN*: cint = SocketMaxConnections.cint
+
+var MSG_PEEK* {.importc: "MSG_PEEK", header: "<sys/socket.h>".}: cint
+var MSG_TRUNC* {.importc: "MSG_TRUNC", header: "<sys/socket.h>".}: cint
+var MSG_WAITALL* {.importc: "MSG_WAITALL", header: "<sys/socket.h>".}: cint
+var AF_INET* {.importc: "AF_INET", header: "<sys/socket.h>".}: cint
+var AF_INET6* {.importc: "AF_INET6", header: "<sys/socket.h>".}: cint
+# var AF_UNIX* {.importc: "AF_UNIX", header: "<sys/socket.h>".}: cint
+const AF_UNIX*: cint = 1 # for compat with Nim libraries, doesn't exist on freertos
+var AF_UNSPEC* {.importc: "AF_UNSPEC", header: "<sys/socket.h>".}: cint
+var SHUT_RD* {.importc: "SHUT_RD", header: "<sys/socket.h>".}: cint
+var SHUT_RDWR* {.importc: "SHUT_RDWR", header: "<sys/socket.h>".}: cint
+var SHUT_WR* {.importc: "SHUT_WR", header: "<sys/socket.h>".}: cint
+
+# # <sys/stat.h>
+# <sys/stat.h>
+
+# var S_IFBLK* {.importc: "S_IFBLK", header: "<sys/stat.h>".}: cint
+# var S_IFCHR* {.importc: "S_IFCHR", header: "<sys/stat.h>".}: cint
+# var S_IFDIR* {.importc: "S_IFDIR", header: "<sys/stat.h>".}: cint
+# var S_IFIFO* {.importc: "S_IFIFO", header: "<sys/stat.h>".}: cint
+# var S_IFLNK* {.importc: "S_IFLNK", header: "<sys/stat.h>".}: cint
+# var S_IFMT* {.importc: "S_IFMT", header: "<sys/stat.h>".}: cint
+# var S_IFREG* {.importc: "S_IFREG", header: "<sys/stat.h>".}: cint
+# var S_IFSOCK* {.importc: "S_IFSOCK", header: "<sys/stat.h>".}: cint
+var S_IRGRP* {.importc: "S_IRGRP", header: "<sys/stat.h>".}: cint
+var S_IROTH* {.importc: "S_IROTH", header: "<sys/stat.h>".}: cint
+var S_IRUSR* {.importc: "S_IRUSR", header: "<sys/stat.h>".}: cint
+# var S_IRWXG* {.importc: "S_IRWXG", header: "<sys/stat.h>".}: cint
+# var S_IRWXO* {.importc: "S_IRWXO", header: "<sys/stat.h>".}: cint
+# var S_IRWXU* {.importc: "S_IRWXU", header: "<sys/stat.h>".}: cint
+# var S_ISGID* {.importc: "S_ISGID", header: "<sys/stat.h>".}: cint
+# var S_ISUID* {.importc: "S_ISUID", header: "<sys/stat.h>".}: cint
+# var S_ISVTX* {.importc: "S_ISVTX", header: "<sys/stat.h>".}: cint
+var S_IWGRP* {.importc: "S_IWGRP", header: "<sys/stat.h>".}: cint
+var S_IWOTH* {.importc: "S_IWOTH", header: "<sys/stat.h>".}: cint
+var S_IWUSR* {.importc: "S_IWUSR", header: "<sys/stat.h>".}: cint
+var S_IXGRP* {.importc: "S_IXGRP", header: "<sys/stat.h>".}: cint
+var S_IXOTH* {.importc: "S_IXOTH", header: "<sys/stat.h>".}: cint
+var S_IXUSR* {.importc: "S_IXUSR", header: "<sys/stat.h>".}: cint
+
+# # <sys/statvfs.h>
+# var ST_RDONLY* {.importc: "ST_RDONLY", header: "<sys/statvfs.h>".}: cint
+# var ST_NOSUID* {.importc: "ST_NOSUID", header: "<sys/statvfs.h>".}: cint
+
+# # <sys/wait.h>
+# var WNOHANG* {.importc: "WNOHANG", header: "<sys/wait.h>".}: cint
+# var WUNTRACED* {.importc: "WUNTRACED", header: "<sys/wait.h>".}: cint
+# var WEXITED* {.importc: "WEXITED", header: "<sys/wait.h>".}: cint
+# var WSTOPPED* {.importc: "WSTOPPED", header: "<sys/wait.h>".}: cint
+# var WCONTINUED* {.importc: "WCONTINUED", header: "<sys/wait.h>".}: cint
+# var WNOWAIT* {.importc: "WNOWAIT", header: "<sys/wait.h>".}: cint
+# var P_ALL* {.importc: "P_ALL", header: "<sys/wait.h>".}: cint
+# var P_PID* {.importc: "P_PID", header: "<sys/wait.h>".}: cint
+# var P_PGID* {.importc: "P_PGID", header: "<sys/wait.h>".}: cint
+
+# # <spawn.h>
+# var POSIX_SPAWN_RESETIDS* {.importc: "POSIX_SPAWN_RESETIDS", header: "<spawn.h>".}: cint
+# var POSIX_SPAWN_SETPGROUP* {.importc: "POSIX_SPAWN_SETPGROUP", header: "<spawn.h>".}: cint
+# var POSIX_SPAWN_SETSCHEDPARAM* {.importc: "POSIX_SPAWN_SETSCHEDPARAM", header: "<spawn.h>".}: cint
+# var POSIX_SPAWN_SETSCHEDULER* {.importc: "POSIX_SPAWN_SETSCHEDULER", header: "<spawn.h>".}: cint
+# var POSIX_SPAWN_SETSIGDEF* {.importc: "POSIX_SPAWN_SETSIGDEF", header: "<spawn.h>".}: cint
+# var POSIX_SPAWN_SETSIGMASK* {.importc: "POSIX_SPAWN_SETSIGMASK", header: "<spawn.h>".}: cint
+
+## <stdio.h>
+# var IOFBF* {.importc: "_IOFBF", header: "<stdio.h>".}: cint
+# var IONBF* {.importc: "_IONBF", header: "<stdio.h>".}: cint
+
+# <time.h>
+var CLOCKS_PER_SEC* {.importc: "CLOCKS_PER_SEC", header: "<time.h>".}: clong
+var CLOCK_PROCESS_CPUTIME_ID* {.importc: "CLOCK_PROCESS_CPUTIME_ID", header: "<time.h>".}: cint
+var CLOCK_THREAD_CPUTIME_ID* {.importc: "CLOCK_THREAD_CPUTIME_ID", header: "<time.h>".}: cint
+var CLOCK_REALTIME* {.importc: "CLOCK_REALTIME", header: "<time.h>".}: cint
+var TIMER_ABSTIME* {.importc: "TIMER_ABSTIME", header: "<time.h>".}: cint
+var CLOCK_MONOTONIC* {.importc: "CLOCK_MONOTONIC", header: "<time.h>".}: cint
+
+# <unistd.h>
+
+const F_OK* = cint(0)
+const R_OK* = cint(4)
+const W_OK* = cint(2)
+const X_OK* = cint(1)
+const F_LOCK* = cint(1)
+const F_TEST* = cint(3)
+const F_TLOCK* = cint(2)
+const F_ULOCK* = cint(0)
+
diff --git a/lib/posix/posix_other.nim b/lib/posix/posix_other.nim
index ed058d5cf88d..1ad05060d47e 100644
--- a/lib/posix/posix_other.nim
+++ b/lib/posix/posix_other.nim
@@ -10,9 +10,14 @@
 when defined(nimHasStyleChecks):
   {.push styleChecks: off.}
 
-const
-  hasSpawnH = true # should exist for every Posix system nowadays
-  hasAioH = defined(linux)
+when defined(freertos):
+  const
+    hasSpawnH = false # should exist for every Posix system nowadays
+    hasAioH = false
+else:
+  const
+    hasSpawnH = true # should exist for every Posix system nowadays
+    hasAioH = defined(linux)
 
 when defined(linux) and not defined(android):
   # On Linux:
@@ -397,21 +402,55 @@ type
   SockLen* {.importc: "socklen_t", header: "<sys/socket.h>".} = cuint
   TSa_Family* {.importc: "sa_family_t", header: "<sys/socket.h>".} = cushort
 
-  SockAddr* {.importc: "struct sockaddr", header: "<sys/socket.h>",
-              pure, final.} = object ## struct sockaddr
-    sa_family*: TSa_Family         ## Address family.
-    sa_data*: array[0..255, char] ## Socket address (variable-length data).
+when defined(lwip):
+  type
+    SockAddr* {.importc: "struct sockaddr", header: "<sys/socket.h>",
+                pure, final.} = object ## struct sockaddr
+      sa_len*: uint8         ## Address family.
+      sa_family*: TSa_Family         ## Address family.
+      sa_data*: array[0..255, char] ## Socket address (variable-length data).
+else:
+  type
+    SockAddr* {.importc: "struct sockaddr", header: "<sys/socket.h>",
+                pure, final.} = object ## struct sockaddr
+      sa_family*: TSa_Family         ## Address family.
+      sa_data*: array[0..255, char] ## Socket address (variable-length data).
 
+type
   Sockaddr_un* {.importc: "struct sockaddr_un", header: "<sys/un.h>",
               pure, final.} = object ## struct sockaddr_un
     sun_family*: TSa_Family         ## Address family.
     sun_path*: array[0..Sockaddr_un_path_length-1, char] ## Socket path
 
-  Sockaddr_storage* {.importc: "struct sockaddr_storage",
-                       header: "<sys/socket.h>",
-                       pure, final.} = object ## struct sockaddr_storage
-    ss_family*: TSa_Family ## Address family.
 
+when defined(lwip):
+  when not defined(lwip6):
+    type
+      Sockaddr_storage* {.importc: "struct sockaddr_storage",
+                          header: "<sys/socket.h>",
+                          pure, final.} = object ## struct sockaddr_storage
+        s2_len*: uint8 ## Address family.
+        ss_family*: TSa_Family ## Address family.
+        s2_data1*: array[2, char] ## Address family.
+        s2_data2*: array[3, uint32] ## Address family.
+  else:
+    type
+      Sockaddr_storage* {.importc: "struct sockaddr_storage",
+                          header: "<sys/socket.h>",
+                          pure, final.} = object ## struct sockaddr_storage
+        s2_len*: uint8 ## Address family.
+        ss_family*: TSa_Family ## Address family.
+        s2_data1*: array[2, char] ## Address family.
+        s2_data2*: array[3, uint32] ## Address family.
+        s2_data3*: array[3, uint32] ## Address family.
+else:
+  type
+    Sockaddr_storage* {.importc: "struct sockaddr_storage",
+                        header: "<sys/socket.h>",
+                        pure, final.} = object ## struct sockaddr_storage
+      ss_family*: TSa_Family ## Address family.
+
+type
   Tif_nameindex* {.importc: "struct if_nameindex", final,
                    pure, header: "<net/if.h>".} = object ## struct if_nameindex
     if_index*: cint   ## Numeric index of the interface.
@@ -530,13 +569,15 @@ type
     ai_canonname*: cstring  ## Canonical name of service location.
     ai_next*: ptr AddrInfo ## Pointer to next in list.
 
-  TPollfd* {.importc: "struct pollfd", pure, final,
-             header: "<poll.h>".} = object ## struct pollfd
-    fd*: cint        ## The following descriptor being polled.
-    events*: cshort  ## The input event flags (see below).
-    revents*: cshort ## The output event flags (see below).
+when not defined(lwip):
+  type
+    TPollfd* {.importc: "struct pollfd", pure, final,
+              header: "<poll.h>".} = object ## struct pollfd
+      fd*: cint        ## The following descriptor being polled.
+      events*: cshort  ## The input event flags (see below).
+      revents*: cshort ## The output event flags (see below).
 
-  Tnfds* {.importc: "nfds_t", header: "<poll.h>".} = cint
+    Tnfds* {.importc: "nfds_t", header: "<poll.h>".} = cint
 
 var
   errno* {.importc, header: "<errno.h>".}: cint ## error variable
@@ -545,7 +586,10 @@ var
   timezone* {.importc, header: "<time.h>".}: int
 
 # Regenerate using detect.nim!
-include posix_other_consts
+when defined(lwip):
+  include posix_freertos_consts
+else:
+  include posix_other_consts
 
 when defined(linux):
   var
diff --git a/lib/pure/ioselects/ioselectors_select.nim b/lib/pure/ioselects/ioselectors_select.nim
index 02a853b42948..2f22f1b305fd 100644
--- a/lib/pure/ioselects/ioselectors_select.nim
+++ b/lib/pure/ioselects/ioselectors_select.nim
@@ -312,7 +312,7 @@ proc selectInto*[T](s: Selector[T], timeout: int,
   verifySelectParams(timeout)
 
   if timeout != -1:
-    when defined(genode):
+    when defined(genode) or defined(freertos):
       tv.tv_sec = Time(timeout div 1_000)
     else:
       tv.tv_sec = timeout.int32 div 1_000
diff --git a/lib/pure/nativesockets.nim b/lib/pure/nativesockets.nim
index 49a1192dfeab..0b0c4b3985e4 100644
--- a/lib/pure/nativesockets.nim
+++ b/lib/pure/nativesockets.nim
@@ -269,7 +269,7 @@ proc getAddrInfo*(address: string, port: Port, domain: Domain = AF_INET,
   let socketPort = if sockType == SOCK_RAW: "" else: $port
   var gaiResult = getaddrinfo(address, socketPort, addr(hints), result)
   if gaiResult != 0'i32:
-    when useWinVersion:
+    when useWinVersion or defined(freertos):
       raiseOSError(osLastError())
     else:
       raiseOSError(osLastError(), $gai_strerror(gaiResult))
diff --git a/lib/pure/selectors.nim b/lib/pure/selectors.nim
index 6007a82501cf..f3726efaab05 100644
--- a/lib/pure/selectors.nim
+++ b/lib/pure/selectors.nim
@@ -332,5 +332,7 @@ else:
     include ioselects/ioselectors_select # TODO: use the native VFS layer
   elif defined(nintendoswitch):
     include ioselects/ioselectors_select
+  elif defined(freertos) or defined(lwip):
+    include ioselects/ioselectors_select
   else:
     include ioselects/ioselectors_poll
diff --git a/lib/system/dyncalls.nim b/lib/system/dyncalls.nim
index a15d9267ff7e..1b0a3e64c229 100644
--- a/lib/system/dyncalls.nim
+++ b/lib/system/dyncalls.nim
@@ -179,7 +179,7 @@ elif defined(genode):
   proc nimGetProcAddr(lib: LibHandle, name: cstring): ProcAddr {.
     error: "nimGetProcAddr not implemented".}
 
-elif defined(nintendoswitch):
+elif defined(nintendoswitch) or defined(freertos):
   proc nimUnloadLibrary(lib: LibHandle) =
     cstderr.rawWrite("nimUnLoadLibrary not implemented")
     cstderr.rawWrite("\n")
diff --git a/lib/system/io.nim b/lib/system/io.nim
index 3d5cf981aba0..c3b2976fbd3a 100644
--- a/lib/system/io.nim
+++ b/lib/system/io.nim
@@ -269,7 +269,7 @@ when SupportIoctlInheritCtl:
 
   proc c_ioctl(fd: cint, request: cint): cint {.
     importc: "ioctl", header: "<sys/ioctl.h>", varargs.}
-elif defined(posix) and not defined(nimscript):
+elif defined(posix) and not defined(lwip) and not defined(nimscript):
   var
     F_GETFD {.importc, header: "<fcntl.h>".}: cint
     F_SETFD {.importc, header: "<fcntl.h>".}: cint
@@ -336,6 +336,8 @@ when defined(nimdoc) or (defined(posix) and not defined(nimscript)) or defined(w
     ## availability with `declared() <system.html#declared,untyped>`.
     when SupportIoctlInheritCtl:
       result = c_ioctl(f, if inheritable: FIONCLEX else: FIOCLEX) != -1
+    elif defined(freertos):
+      result = true
     elif defined(posix):
       var flags = c_fcntl(f, F_GETFD)
       if flags == -1:
@@ -767,6 +769,10 @@ when declared(stdout):
     var echoLock: SysLock
     initSysLock echoLock
 
+  const stdOutLock = not defined(windows) and not defined(android) and
+                     not defined(nintendoswitch) and not defined(freertos) and
+                     hostOS != "any"
+
   proc echoBinSafe(args: openArray[string]) {.compilerproc.} =
     when defined(androidNDK):
       var s = ""
@@ -775,7 +781,7 @@ when declared(stdout):
       android_log_print(ANDROID_LOG_VERBOSE, "nim", s)
     else:
       # flockfile deadlocks some versions of Android 5.x.x
-      when not defined(windows) and not defined(android) and not defined(nintendoswitch) and hostOS != "any":
+      when stdOutLock:
         proc flockfile(f: File) {.importc, nodecl.}
         proc funlockfile(f: File) {.importc, nodecl.}
         flockfile(stdout)
@@ -789,7 +795,7 @@ when declared(stdout):
       const linefeed = "\n"
       discard c_fwrite(linefeed.cstring, linefeed.len, 1, stdout)
       discard c_fflush(stdout)
-      when not defined(windows) and not defined(android) and not defined(nintendoswitch) and hostOS != "any":
+      when stdOutLock:
         funlockfile(stdout)
       when defined(windows) and compileOption("threads"):
         releaseSys echoLock
diff --git a/tools/kochdocs.nim b/tools/kochdocs.nim
index 05ddb4f1ebcb..453b1037b9c6 100644
--- a/tools/kochdocs.nim
+++ b/tools/kochdocs.nim
@@ -158,6 +158,7 @@ lib/posix/posix_nintendoswitch_consts.nim
 lib/posix/posix_linux_amd64.nim
 lib/posix/posix_linux_amd64_consts.nim
 lib/posix/posix_other_consts.nim
+lib/posix/posix_freertos_consts.nim
 lib/posix/posix_openbsd_amd64.nim
 lib/posix/posix_haiku.nim
 lib/js/jsre.nim