new file mode 100644
--- /dev/null
+++ b/src/os/win32/ngx_wsasend_chain.c
@@ -0,0 +1,181 @@
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+
+
+ngx_chain_t *ngx_wsasend_chain(ngx_connection_t *c, ngx_chain_t *in)
+{
+    int               rc;
+    char             *prev;
+    size_t            size, sent;
+    LPWSABUF          wsabuf;
+    ngx_err_t         err;
+    ngx_event_t      *wev;
+    ngx_array_t       wsabufs;
+    ngx_chain_t      *ce;
+    LPWSAOVERLAPPED   ovlp;
+
+#if 0
+
+iocp:
+    if ready
+       get result
+       update chain
+       return if done;
+    wsasend
+
+non-block
+    for ( ;; ) {
+       wsasend
+       if no again
+          update chain
+          return if done;
+    }
+
+
+    for ( ;; ) {
+
+        make buffers and limit data for both ovlp and nonblocked,
+                     configured in events module
+
+        if (iocp && ready) {
+            get result
+
+        } else {
+            if (file)
+                transmitfile
+            else
+                wsasend
+
+            if (iocp)
+                return chain
+            return chain if again
+            here is result
+        }
+
+        if (result)
+            update chain;
+            return chain if done
+        }
+    }
+
+
+#endif
+
+    wev = c->write;
+
+    if (((ngx_event_flags & NGX_HAVE_AIO_EVENT) && !wev->ready)
+        || ((ngx_event_flags & NGX_HAVE_AIO_EVENT) == 0))
+    {
+        /*
+         * WSABUFs must be 4-byte aligned otherwise
+         * WSASend() will return undocumented WSAEINVAL error.
+         */
+
+        ngx_init_array(wsabufs, c->pool, 10, sizeof(WSABUF), NGX_CHAIN_ERROR);
+
+        prev = NULL;
+        wsabuf = NULL;
+
+        /* create the WSABUF and coalesce the neighbouring chain entries */
+        for (ce = in; ce; ce = ce->next) {
+
+            if (prev == ce->hunk->pos) {
+                wsabuf->len += ce->hunk->last - ce->hunk->pos;
+                prev = ce->hunk->last;
+
+            } else {
+                ngx_test_null(wsabuf, ngx_push_array(&wsabufs),
+                              NGX_CHAIN_ERROR);
+                wsabuf->buf = ce->hunk->pos;
+                wsabuf->len = ce->hunk->last - ce->hunk->pos;
+                prev = ce->hunk->last;
+            }
+        }
+
+        if (ngx_event_flags & NGX_HAVE_AIO_EVENT) {
+            ovlp = (LPWSAOVERLAPPED) &c->write->ovlp;
+            ngx_memzero(ovlp, sizeof(WSAOVERLAPPED));
+
+        } else {
+            ovlp = NULL;
+        }
+
+        rc = WSASend(c->fd, wsabufs.elts, wsabufs.nelts, &sent, 0, ovlp, NULL);
+
+        if (rc == -1) {
+            err = ngx_errno;
+            if (err == WSA_IO_PENDING) {
+                sent = 0;
+
+            } else if (err == WSAEWOULDBLOCK) {
+                sent = 0;
+                ngx_log_error(NGX_LOG_INFO, c->log, err, "WSASend() EAGAIN");
+
+            } else {
+                ngx_log_error(NGX_LOG_CRIT, c->log, err, "WSASend() failed");
+                return NGX_CHAIN_ERROR;
+            }
+
+        } else {
+
+            if (ngx_event_flags & NGX_HAVE_IOCP_EVENT) {
+
+                /*
+                 * If a socket was bound with I/O completion port then
+                 * GetQueuedCompletionStatus() would anyway return its status
+                 * despite that WSASend() was already completed.
+                 */
+
+                sent = 0;
+            }
+        }
+
+    } else {
+        if (ngx_event_flags & NGX_HAVE_IOCP_EVENT) {
+            wev->ready = 0;
+
+            /* the overlapped WSASend() completed */
+
+            if (wev->ovlp.error) {
+                ngx_log_error(NGX_LOG_ERR, c->log, wev->ovlp.error,
+                              "WSASend() failed");
+                return NGX_CHAIN_ERROR;
+            }
+
+            sent = wev->available;
+        }
+    }
+
+#if (NGX_DEBUG_WRITE_CHAIN)
+    ngx_log_debug(c->log, "WSASend(): %d" _ sent);
+#endif
+
+    c->sent += sent;
+
+    for (ce = in; ce && sent > 0; ce = ce->next) {
+
+        size = ce->hunk->last - ce->hunk->pos;
+
+        if (sent >= size) {
+            sent -= size;
+
+            if (ce->hunk->type & NGX_HUNK_IN_MEMORY) {
+                ce->hunk->pos = ce->hunk->last;
+            }
+
+            continue;
+        }
+
+        if (ce->hunk->type & NGX_HUNK_IN_MEMORY) {
+            ce->hunk->pos += sent;
+        }
+
+        break;
+    }
+
+    ngx_destroy_array(&wsabufs);
+
+    return ce;
+}