diff --git a/.wolfssl_known_macro_extras b/.wolfssl_known_macro_extras
index d399da0aea..c7ce71064e 100644
--- a/.wolfssl_known_macro_extras
+++ b/.wolfssl_known_macro_extras
@@ -947,6 +947,7 @@ __SUNPRO_CC
 __SVR4
 __TI_COMPILER_VERSION__
 __TURBOC__
+__UNIX__
 __USE_GNU
 __USE_MISC
 __USE_XOPEN2K
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4a9486c673..dfe891bca6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2419,12 +2419,15 @@ target_include_directories(wolfssl
 
 target_link_libraries(wolfssl PUBLIC ${WOLFSSL_LINK_LIBS})
 
-if (WIN32 OR ${CMAKE_SYSTEM_NAME} MATCHES "^MSYS" OR ${CMAKE_SYSTEM_NAME} MATCHES "^MINGW")
+if(CMAKE_C_COMPILER_ID STREQUAL "OpenWatcom")
+    if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+        target_link_libraries(wolfssl PUBLIC ws2_32 crypt32)
+    endif()
+elseif (WIN32 OR ${CMAKE_SYSTEM_NAME} MATCHES "^MSYS" OR ${CMAKE_SYSTEM_NAME} MATCHES "^MINGW")
     # For Windows link required libraries
     message("Building on Windows/MSYS/MINGW")
     target_link_libraries(wolfssl PUBLIC
         ws2_32 crypt32 advapi32)
-elseif(CMAKE_C_COMPILER_ID STREQUAL "OpenWatcom")
 elseif(APPLE)
     message("Building on Apple")
     if(WOLFSSL_SYS_CA_CERTS)
diff --git a/src/wolfio.c b/src/wolfio.c
index ab99a891c2..e63595a550 100644
--- a/src/wolfio.c
+++ b/src/wolfio.c
@@ -1251,6 +1251,9 @@ int wolfIO_SendTo(SOCKET_T sd, WOLFSSL_BIO_ADDR *addr, char *buf, int sz, int wr
         ret = ioctlsocket(sockfd, FIONBIO, &blocking);
         if (ret == SOCKET_ERROR)
             ret = WOLFSSL_FATAL_ERROR;
+    #elif defined(__WATCOMC__) && defined(__OS2__)
+        if (ioctl(sockfd, FIONBIO, &non_blocking) == -1)
+            ret = WOLFSSL_FATAL_ERROR;
     #else
         ret = fcntl(sockfd, F_GETFL, 0);
         if (ret >= 0) {
@@ -1290,9 +1293,9 @@ int wolfIO_SendTo(SOCKET_T sd, WOLFSSL_BIO_ADDR *addr, char *buf, int sz, int wr
 
         ret = select(nfds, &rfds, &wfds, NULL, &timeout);
         if (ret == 0) {
-        #ifdef DEBUG_HTTP
+    #ifdef DEBUG_HTTP
             fprintf(stderr, "Timeout: %d\n", ret);
-        #endif
+    #endif
             return HTTP_TIMEOUT;
         }
         else if (ret > 0) {
diff --git a/wolfcrypt/benchmark/benchmark.c b/wolfcrypt/benchmark/benchmark.c
index fe482d6266..fa308dfcad 100644
--- a/wolfcrypt/benchmark/benchmark.c
+++ b/wolfcrypt/benchmark/benchmark.c
@@ -14997,6 +14997,14 @@ void bench_sphincsKeySign(byte level, byte optim)
         return (double)us / 1000000.0;
     }
 
+#elif defined(__WATCOMC__)
+
+    #include <time.h>
+    WC_INLINE double current_time(int reset)
+    {
+        (void)reset;
+        return ((double)clock())/CLOCKS_PER_SEC;
+    }
 #else
 
     #include <time.h>
diff --git a/wolfssl/test.h b/wolfssl/test.h
index 6fa29344b8..fa84ab0e00 100644
--- a/wolfssl/test.h
+++ b/wolfssl/test.h
@@ -85,11 +85,50 @@
     #endif /* HAVE_ECC */
 #endif /*HAVE_PK_CALLBACKS */
 
-#ifdef USE_WINDOWS_API
+#ifdef __WATCOMC__
+    #define SNPRINTF snprintf
+    #if defined(__NT__)
+        #include <winsock2.h>
+        #include <ws2tcpip.h>
+        #include <process.h>
+        #ifdef TEST_IPV6            /* don't require newer SDK for IPV4 */
+            #include <wspiapi.h>
+        #endif
+        #define SOCKET_T SOCKET
+        #define XSLEEP_MS(t) Sleep(t)
+    #elif defined(__OS2__)
+        #include <netdb.h>
+        #include <sys/ioctl.h>
+        #include <tcpustd.h>
+        #define SOCKET_T int
+    #elif defined(__UNIX__)
+        #include <string.h>
+        #include <netdb.h>
+        #include <netinet/tcp.h>
+        #ifndef WOLFSSL_NDS
+            #include <sys/ioctl.h>
+        #endif
+        #include <time.h>
+        #include <sys/time.h>
+        #ifdef HAVE_PTHREAD
+            #include <pthread.h>
+        #endif
+        #define SOCKET_T int
+        #ifndef SO_NOSIGPIPE
+            #include <signal.h>  /* ignore SIGPIPE */
+        #endif
+
+        #define XSLEEP_MS(m) \
+            { \
+                struct timespec req = { (m)/1000, ((m) % 1000) * 1000 }; \
+                nanosleep( &req, NULL ); \
+            }
+    #endif
+#elif defined(USE_WINDOWS_API)
     #include <winsock2.h>
+    #include <ws2tcpip.h>
     #include <process.h>
     #ifdef TEST_IPV6            /* don't require newer SDK for IPV4 */
-        #include <ws2tcpip.h>
         #include <wspiapi.h>
     #endif
     #define SOCKET_T SOCKET
@@ -1429,7 +1468,7 @@ static WC_INLINE void tcp_socket(SOCKET_T* sockfd, int udp, int sctp)
         err_sys_with_errno("socket failed\n");
     }
 
-#ifndef USE_WINDOWS_API
+#if !defined(USE_WINDOWS_API) && !defined(__WATCOMC__) && !defined(__OS2__)
 #ifdef SO_NOSIGPIPE
     {
         int       on = 1;
@@ -1457,7 +1496,7 @@ static WC_INLINE void tcp_socket(SOCKET_T* sockfd, int udp, int sctp)
             err_sys_with_errno("setsockopt TCP_NODELAY failed\n");
     }
 #endif
-#endif  /* USE_WINDOWS_API */
+#endif  /* !defined(USE_WINDOWS_API) && !defined(__WATCOMC__) && ... */
 }
 
 #if defined(WOLFSSL_WOLFSENTRY_HOOKS) && defined(WOLFSENTRY_H)
@@ -1801,6 +1840,10 @@ static WC_INLINE void tcp_set_nonblocking(SOCKET_T* sockfd)
         || defined (WOLFSSL_TIRTOS)|| defined(WOLFSSL_VXWORKS) \
         || defined(WOLFSSL_ZEPHYR)
          /* non blocking not supported, for now */
+    #elif defined(__WATCOMC__) && defined(__OS2__)
+        int blocking = 1;
+        if (ioctl(*sockfd, FIONBIO, &blocking) == -1)
+            err_sys_with_errno("ioctl failed");
     #else
         int flags = fcntl(*sockfd, F_GETFL, 0);
         if (flags < 0)
@@ -1822,6 +1865,10 @@ static WC_INLINE void tcp_set_blocking(SOCKET_T* sockfd)
         || defined (WOLFSSL_TIRTOS)|| defined(WOLFSSL_VXWORKS) \
         || defined(WOLFSSL_ZEPHYR)
          /* non blocking not supported, for now */
+    #elif defined(__WATCOMC__) && defined(__OS2__)
+        int blocking = 0;
+        if (ioctl(*sockfd, FIONBIO, &blocking) == -1)
+            err_sys_with_errno("ioctl failed");
     #else
         int flags = fcntl(*sockfd, F_GETFL, 0);
         if (flags < 0)
diff --git a/wolfssl/wolfcrypt/ecc.h b/wolfssl/wolfcrypt/ecc.h
index 3d5e939d91..04a7a66e94 100644
--- a/wolfssl/wolfcrypt/ecc.h
+++ b/wolfssl/wolfcrypt/ecc.h
@@ -287,7 +287,8 @@ typedef byte   ecc_oid_t;
 #endif
 
 
-#if !defined(WOLFSSL_ECC_CURVE_STATIC) && defined(USE_WINDOWS_API)
+#if !defined(WOLFSSL_ECC_CURVE_STATIC) && defined(USE_WINDOWS_API) && \
+        !defined(__WATCOMC__)
     /* MSC does something different with the pointers to the arrays than GCC,
      * and it causes the FIPS checksum to fail. In the case of windows builds,
      * store everything as arrays instead of pointers to strings. */
diff --git a/wolfssl/wolfcrypt/types.h b/wolfssl/wolfcrypt/types.h
index 498c807aa1..a87a309ab5 100644
--- a/wolfssl/wolfcrypt/types.h
+++ b/wolfssl/wolfcrypt/types.h
@@ -922,6 +922,13 @@ typedef struct w64wrapper {
             /* use only Thread Safe version of strtok */
             #if defined(USE_WOLF_STRTOK)
                 #define XSTRTOK(s1,d,ptr) wc_strtok((s1),(d),(ptr))
+            #elif defined(__WATCOMC__)
+                #if __WATCOMC__ < 1300
+                    #define USE_WOLF_STRTOK
+                    #define XSTRTOK(s1,d,ptr) wc_strtok((s1),(d),(ptr))
+                #else
+                    #define XSTRTOK(s1,d,ptr) strtok_r((s1),(d),(ptr))
+                #endif
             #elif defined(USE_WINDOWS_API) || defined(INTIME_RTOS)
                 #define XSTRTOK(s1,d,ptr) strtok_s((s1),(d),(ptr))
             #else
@@ -1503,6 +1510,7 @@ typedef struct w64wrapper {
             #define WOLFSSL_THREAD __stdcall
             #define WOLFSSL_THREAD_NO_JOIN _WCCALLBACK
         #elif defined(__OS2__)
+            #define WOLFSSL_THREAD_VOID_RETURN
             typedef void          THREAD_RETURN;
             typedef TID           THREAD_TYPE;
             typedef struct COND_TYPE {
diff --git a/wolfssl/wolfcrypt/visibility.h b/wolfssl/wolfcrypt/visibility.h
index b8eb035e4a..aa506ba21d 100644
--- a/wolfssl/wolfcrypt/visibility.h
+++ b/wolfssl/wolfcrypt/visibility.h
@@ -51,8 +51,15 @@
         #define WOLFSSL_LOCAL
     #endif /* HAVE_VISIBILITY */
 #else /* BUILDING_WOLFSSL */
-    #if defined(_MSC_VER) || defined(__MINGW32__) || defined(__CYGWIN__) || \
-        defined(_WIN32_WCE) || defined(__WATCOMC__)
+    #if defined(__WATCOMC__)
+        #if defined(WOLFSSL_DLL) && defined(__NT__)
+            #define WOLFSSL_API __declspec(dllimport)
+        #else
+            #define WOLFSSL_API
+        #endif
+        #define WOLFSSL_LOCAL
+    #elif defined(_MSC_VER) || defined(__MINGW32__) || defined(__CYGWIN__) || \
+        defined(_WIN32_WCE)
         #if defined(WOLFSSL_DLL)
             #define WOLFSSL_API __declspec(dllimport)
         #else
diff --git a/wolfssl/wolfcrypt/wc_port.h b/wolfssl/wolfcrypt/wc_port.h
index 29e30e6172..b53c1586f6 100644
--- a/wolfssl/wolfcrypt/wc_port.h
+++ b/wolfssl/wolfcrypt/wc_port.h
@@ -120,13 +120,31 @@
 #endif
 
 /* THREADING/MUTEX SECTION */
-#if defined(__WATCOMC__)
-    #if !defined(SINGLE_THREADED)
+#if defined(SINGLE_THREADED) && defined(NO_FILESYSTEM)
+    /* No system headers required for build. */
+#elif defined(__WATCOMC__)
+    #if defined(SINGLE_THREADED)
         #if defined(USE_WINDOWS_API)
             #define _WINSOCKAPI_ /* block inclusion of winsock.h header file */
             #include <windows.h>
-            #undef _WINSOCKAPI_ /* undefine it for MINGW winsock2.h header file */
+            #undef _WINSOCKAPI_ /* undefine it for MINGW winsock2.h header */
+            #ifndef WOLFSSL_USER_IO
+                #include <winsock2.h>
+                #include <ws2tcpip.h> /* required for InetPton */
+            #endif
+        #elif defined(__OS2__)
+            #include <os2.h>
+        #endif
+    #else
+        #if defined(USE_WINDOWS_API)
+            #define _WINSOCKAPI_ /* block inclusion of winsock.h header file */
+            #include <windows.h>
+            #undef _WINSOCKAPI_ /* undefine it for MINGW winsock2.h header */
             #include <process.h>
+            #ifndef WOLFSSL_USER_IO
+                #include <winsock2.h>
+                #include <ws2tcpip.h> /* required for InetPton */
+            #endif
         #elif defined(__OS2__)
             #define INCL_DOSSEMAPHORES
             #define INCL_DOSPROCESS
@@ -140,17 +158,7 @@
                 #include <pthread.h>
             #endif
         #endif
-    #else
-        #if defined(USE_WINDOWS_API)
-            #define _WINSOCKAPI_ /* block inclusion of winsock.h header file */
-            #include <windows.h>
-            #undef _WINSOCKAPI_ /* undefine it for MINGW winsock2.h header file */
-        #elif defined(__OS2__)
-            #include <os2.h>
-        #endif
     #endif
-#elif defined(SINGLE_THREADED) && defined(NO_FILESYSTEM)
-    /* No system headers required for build. */
 #elif defined(USE_WINDOWS_API)
     #if defined(WOLFSSL_PTHREADS)
         #include <pthread.h>
@@ -164,7 +172,7 @@
         #if !defined(WOLFSSL_SGX) && !defined(WOLFSSL_NOT_WINDOWS_API)
             #define _WINSOCKAPI_ /* block inclusion of winsock.h header file. */
             #include <windows.h>
-            #undef _WINSOCKAPI_ /* undefine it for MINGW winsock2.h header file */
+            #undef _WINSOCKAPI_ /* undefine it for MINGW winsock2.h header */
             #ifndef WOLFSSL_USER_IO
                 #include <winsock2.h>
                 #include <ws2tcpip.h> /* required for InetPton */
@@ -926,7 +934,25 @@ WOLFSSL_ABI WOLFSSL_API int wolfCrypt_Cleanup(void);
 
     #if !defined(NO_WOLFSSL_DIR)\
         && !defined(WOLFSSL_NUCLEUS) && !defined(WOLFSSL_NUCLEUS_1_2)
-        #if defined(USE_WINDOWS_API)
+        #if defined(__WATCOMC__)
+            #include <unistd.h>
+            #include <sys/stat.h>
+            #define XWRITE      write
+            #define XREAD       read
+            #define XCLOSE      close
+            #define XSTAT       stat
+            #define XS_ISREG(s) S_ISREG(s)
+            #if defined(__UNIX__)
+                #include <dirent.h>
+                #define SEPARATOR_CHAR ':'
+            #else
+                #include <direct.h>
+                #define SEPARATOR_CHAR ';'
+            #endif
+            #if defined(__NT__)
+                #define XALTHOMEVARNAME "USERPROFILE"
+            #endif
+        #elif defined(USE_WINDOWS_API)
             #include <io.h>
             #include <sys/stat.h>
             #ifndef XSTAT
@@ -964,9 +990,7 @@ WOLFSSL_ABI WOLFSSL_API int wolfCrypt_Cleanup(void);
             #define SEPARATOR_CHAR ':'
 
         #else
-            #ifndef NO_WOLFSSL_DIR
-                #include <dirent.h>
-            #endif
+            #include <dirent.h>
             #include <unistd.h>
             #include <sys/stat.h>
             #define XWRITE      write
diff --git a/wolfssl/wolfio.h b/wolfssl/wolfio.h
index 2e460f5f4f..de45a18b5e 100644
--- a/wolfssl/wolfio.h
+++ b/wolfssl/wolfio.h
@@ -57,7 +57,32 @@
     #include "zlib.h"
 #endif
 
-#ifndef USE_WINDOWS_API
+#if defined(__WATCOMC__)
+    #if defined(__NT__)
+    #elif defined(__OS2__)
+        #include <errno.h>
+        #include <os2.h>
+        #include <sys/types.h>
+        #include <os2/types.h>
+        #include <sys/socket.h>
+        #include <arpa/inet.h>
+        #include <netinet/in.h>
+        #include <nerrno.h>
+        #include <sys/ioctl.h>
+
+        typedef int socklen_t;
+    #elif defined(__LINUX__)
+        #include <sys/types.h>
+        #include <errno.h>
+        #include <unistd.h>
+        #include <fcntl.h>
+        #define XFCNTL(fd, flag, block) fcntl((fd), (flag), (block))
+        #include <sys/socket.h>
+        #include <arpa/inet.h>
+        #include <netinet/in.h>
+    #endif
+#elif defined(USE_WINDOWS_API)
+#else
     #if defined(WOLFSSL_LWIP) && !defined(WOLFSSL_APACHE_MYNEWT)
         /* lwIP needs to be configured to use sockets API in this mode */
         /* LWIP_SOCKET 1 in lwip/opt.h or in build */
@@ -152,26 +177,6 @@
         #include <fclfcntl.h>
     #elif defined(WOLFSSL_EMNET)
         #include <IP/IP.h>
-    #elif defined(__WATCOMC__)
-        #if defined(__OS2__)
-            #include <errno.h>
-            #include <os2.h>
-            #include <sys/types.h>
-            #include <os2/types.h>
-            #include <sys/socket.h>
-            #include <arpa/inet.h>
-            #include <netinet/in.h>
-            #include <nerrno.h>
-
-            typedef int socklen_t;
-        #elif defined(__LINUX__)
-            #include <sys/types.h>
-            #include <errno.h>
-            #include <unistd.h>
-            #include <sys/socket.h>
-            #include <arpa/inet.h>
-            #include <netinet/in.h>
-        #endif
     #elif !defined(WOLFSSL_NO_SOCK)
         #include <sys/types.h>
         #include <errno.h>
@@ -224,7 +229,40 @@
 #define SOCKET_RECEIVING 1
 #define SOCKET_SENDING 2
 
-#ifdef USE_WINDOWS_API
+#ifdef __WATCOMC__
+    #if defined(__NT__)
+        /* no epipe yet */
+        #ifndef WSAEPIPE
+            #define WSAEPIPE       -12345
+        #endif
+        #define SOCKET_EWOULDBLOCK WSAEWOULDBLOCK
+        #define SOCKET_EAGAIN      WSAETIMEDOUT
+        #define SOCKET_ETIMEDOUT   WSAETIMEDOUT
+        #define SOCKET_ECONNRESET  WSAECONNRESET
+        #define SOCKET_EINTR       WSAEINTR
+        #define SOCKET_EPIPE       WSAEPIPE
+        #define SOCKET_ECONNREFUSED WSAENOTCONN
+        #define SOCKET_ECONNABORTED WSAECONNABORTED
+    #elif defined(__OS2__)
+        #define SOCKET_EWOULDBLOCK SOCEWOULDBLOCK
+        #define SOCKET_EAGAIN      SOCEAGAIN
+        #define SOCKET_ETIMEDOUT   SOCETIMEDOUT
+        #define SOCKET_ECONNRESET  SOCECONNRESET
+        #define SOCKET_EINTR       SOCEINTR
+        #define SOCKET_EPIPE       SOCEPIPE
+        #define SOCKET_ECONNREFUSED SOCECONNREFUSED
+        #define SOCKET_ECONNABORTED SOCECONNABORTED
+    #elif defined(__UNIX__)
+        #define SOCKET_EWOULDBLOCK EWOULDBLOCK
+        #define SOCKET_EAGAIN      EAGAIN
+        #define SOCKET_ETIMEDOUT   ETIMEDOUT
+        #define SOCKET_ECONNRESET  ECONNRESET
+        #define SOCKET_EINTR       EINTR
+        #define SOCKET_EPIPE       EPIPE
+        #define SOCKET_ECONNREFUSED ECONNREFUSED
+        #define SOCKET_ECONNABORTED ECONNABORTED
+    #endif
+#elif defined(USE_WINDOWS_API)
     /* no epipe yet */
     #ifndef WSAEPIPE
         #define WSAEPIPE       -12345
@@ -856,21 +894,36 @@ WOLFSSL_API void wolfSSL_SetIOWriteFlags(WOLFSSL* ssl, int flags);
 
 
 #ifndef XINET_NTOP
-    #define XINET_NTOP(a,b,c,d) inet_ntop((a),(b),(c),(d))
-    #ifdef USE_WINDOWS_API /* Windows-friendly definition */
-        #undef  XINET_NTOP
+    #if defined(__WATCOMC__)
+        #if defined(__OS2__) || defined(__NT__) && \
+                (NTDDI_VERSION >= NTDDI_VISTA)
+            #define XINET_NTOP(a,b,c,d) inet_ntop((a),(b),(c),(d))
+        #else
+            #define XINET_NTOP(a,b,c,d) \
+                strncpy((c),inet_ntoa(*(unsigned *)(b)),(d))
+        #endif
+    #elif defined(USE_WINDOWS_API) /* Windows-friendly definition */
         #define XINET_NTOP(a,b,c,d) InetNtop((a),(b),(c),(d))
+    #else
+        #define XINET_NTOP(a,b,c,d) inet_ntop((a),(b),(c),(d))
     #endif
 #endif
 #ifndef XINET_PTON
-    #define XINET_PTON(a,b,c)   inet_pton((a),(b),(c))
-    #ifdef USE_WINDOWS_API /* Windows-friendly definition */
-        #undef  XINET_PTON
+    #if defined(__WATCOMC__)
+        #if defined(__OS2__) || defined(__NT__) && \
+                (NTDDI_VERSION >= NTDDI_VISTA)
+            #define XINET_PTON(a,b,c)   inet_pton((a),(b),(c))
+        #else
+            #define XINET_PTON(a,b,c)   *(unsigned *)(c) = inet_addr((b))
+        #endif
+    #elif defined(USE_WINDOWS_API) /* Windows-friendly definition */
         #if defined(__MINGW64__) && !defined(UNICODE)
             #define XINET_PTON(a,b,c)   InetPton((a),(b),(c))
         #else
             #define XINET_PTON(a,b,c)   InetPton((a),(PCWSTR)(b),(c))
         #endif
+    #else
+        #define XINET_PTON(a,b,c)   inet_pton((a),(b),(c))
     #endif
 #endif