diff --git a/dlls/ntdll/unix/socket.c b/dlls/ntdll/unix/socket.c
index 2f8bd6e62bf..62920a7e557 100644
--- a/dlls/ntdll/unix/socket.c
+++ b/dlls/ntdll/unix/socket.c
@@ -868,11 +868,13 @@ static NTSTATUS sock_send( HANDLE handle, HANDLE event, PIO_APC_ROUTINE apc, voi
                            const struct WS_sockaddr *addr, unsigned int addr_len, int unix_flags, int force_async )
 {
     struct async_send_ioctl *async;
+    ULONG_PTR information;
     HANDLE wait_handle;
     DWORD async_size;
     NTSTATUS status;
     unsigned int i;
     ULONG options;
+    BOOL nonblocking, alerted;
 
     async_size = offsetof( struct async_send_ioctl, iov[count] );
 
@@ -925,16 +927,38 @@ static NTSTATUS sock_send( HANDLE handle, HANDLE event, PIO_APC_ROUTINE apc, voi
         status = wine_server_call( req );
         wait_handle = wine_server_ptr_handle( reply->wait );
         options     = reply->options;
-        if ((!NT_ERROR(status) || wait_handle) && status != STATUS_PENDING)
-        {
-            io->Status = status;
-            io->Information = async->sent_len;
-        }
+        nonblocking = reply->nonblocking;
     }
     SERVER_END_REQ;
 
-    if (status != STATUS_PENDING) release_fileio( &async->io );
+    alerted = status == STATUS_ALERTED;
+    if (alerted)
+    {
+        status = try_send( fd, async );
+        if (status == STATUS_DEVICE_NOT_READY && (force_async || !nonblocking))
+            status = STATUS_PENDING;
 
+        /* If we had a short write and the socket is nonblocking (and we are
+         * not trying to force the operation to be asynchronous), return
+         * success.  Windows actually refuses to send any data in this case,
+         * and returns EWOULDBLOCK, but we have no way of doing that. */
+        if (status == STATUS_DEVICE_NOT_READY && async->sent_len)
+            status = STATUS_SUCCESS;
+    }
+
+    if (status != STATUS_PENDING)
+    {
+        information = async->sent_len;
+        if (!NT_ERROR(status) || (wait_handle && !alerted))
+        {
+            io->Status = status;
+            io->Information = information;
+        }
+        release_fileio( &async->io );
+    }
+    else information = 0;
+
+    if (alerted) set_async_direct_result( &wait_handle, status, information, FALSE );
     if (wait_handle) status = wait_async( wait_handle, options & FILE_SYNCHRONOUS_IO_ALERT );
     return status;
 }
@@ -1055,7 +1079,9 @@ static NTSTATUS sock_transmit( HANDLE handle, HANDLE event, PIO_APC_ROUTINE apc,
     socklen_t addr_len;
     HANDLE wait_handle;
     NTSTATUS status;
+    ULONG_PTR information;
     ULONG options;
+    BOOL alerted;
 
     addr_len = sizeof(addr);
     if (getpeername( fd, &addr.addr, &addr_len ) != 0)
@@ -1105,16 +1131,40 @@ static NTSTATUS sock_transmit( HANDLE handle, HANDLE event, PIO_APC_ROUTINE apc,
         status = wine_server_call( req );
         wait_handle = wine_server_ptr_handle( reply->wait );
         options     = reply->options;
-        /* In theory we'd fill the iosb here, as above in sock_send(), but it's
-         * actually currently impossible to get STATUS_SUCCESS. The server will
-         * either return STATUS_PENDING or an error code, and in neither case
-         * should the iosb be filled. */
-        if (!status) FIXME( "Unhandled success status." );
     }
     SERVER_END_REQ;
 
-    if (status != STATUS_PENDING) release_fileio( &async->io );
+    alerted = status == STATUS_ALERTED;
+    if (alerted)
+    {
+        status = try_transmit( fd, file_fd, async );
+        if (status == STATUS_DEVICE_NOT_READY)
+            status = STATUS_PENDING;
+    }
 
+    if (status != STATUS_PENDING)
+    {
+        information = async->head_cursor + async->file_cursor + async->tail_cursor;
+        if (!NT_ERROR(status) || wait_handle)
+        {
+            io->Status = status;
+            io->Information = information;
+        }
+        release_fileio( &async->io );
+    }
+    else information = 0;
+
+    if (alerted)
+    {
+        set_async_direct_result( &wait_handle, status, information, TRUE );
+        if (!(options & (FILE_SYNCHRONOUS_IO_ALERT | FILE_SYNCHRONOUS_IO_NONALERT)))
+        {
+            /* Pretend we always do async I/O.  The client can always retrieve
+             * the actual I/O status via the IO_STATUS_BLOCK.
+             */
+            status = STATUS_PENDING;
+        }
+    }
     if (wait_handle) status = wait_async( wait_handle, options & FILE_SYNCHRONOUS_IO_ALERT );
     return status;
 }
diff --git a/include/wine/server_protocol.h b/include/wine/server_protocol.h
index 75b48d7601c..b3a5d3ef3d5 100644
--- a/include/wine/server_protocol.h
+++ b/include/wine/server_protocol.h
@@ -1791,6 +1791,8 @@ struct send_socket_reply
     struct reply_header __header;
     obj_handle_t wait;
     unsigned int options;
+    int          nonblocking;
+    char __pad_20[4];
 };
 
 
@@ -6284,7 +6286,7 @@ union generic_reply
 
 /* ### protocol_version begin ### */
 
-#define SERVER_PROTOCOL_VERSION 747
+#define SERVER_PROTOCOL_VERSION 748
 
 /* ### protocol_version end ### */
 
diff --git a/server/protocol.def b/server/protocol.def
index 66c6c97b1e0..81b44aefd7c 100644
--- a/server/protocol.def
+++ b/server/protocol.def
@@ -1467,6 +1467,7 @@ enum server_fd_type
 @REPLY
     obj_handle_t wait;          /* handle to wait on for blocking send */
     unsigned int options;       /* device open options */
+    int          nonblocking;   /* is socket non-blocking? */
 @END
 
 
diff --git a/server/request.h b/server/request.h
index 434041490c0..32929c146a0 100644
--- a/server/request.h
+++ b/server/request.h
@@ -1056,7 +1056,8 @@ C_ASSERT( FIELD_OFFSET(struct send_socket_request, total) == 60 );
 C_ASSERT( sizeof(struct send_socket_request) == 64 );
 C_ASSERT( FIELD_OFFSET(struct send_socket_reply, wait) == 8 );
 C_ASSERT( FIELD_OFFSET(struct send_socket_reply, options) == 12 );
-C_ASSERT( sizeof(struct send_socket_reply) == 16 );
+C_ASSERT( FIELD_OFFSET(struct send_socket_reply, nonblocking) == 16 );
+C_ASSERT( sizeof(struct send_socket_reply) == 24 );
 C_ASSERT( FIELD_OFFSET(struct get_next_console_request_request, handle) == 12 );
 C_ASSERT( FIELD_OFFSET(struct get_next_console_request_request, signal) == 16 );
 C_ASSERT( FIELD_OFFSET(struct get_next_console_request_request, read) == 20 );
diff --git a/server/sock.c b/server/sock.c
index 3e140319965..1beff85cbe0 100644
--- a/server/sock.c
+++ b/server/sock.c
@@ -3526,6 +3526,25 @@ DECL_HANDLER(send_socket)
     if ((status == STATUS_PENDING || status == STATUS_DEVICE_NOT_READY) && sock->wr_shutdown)
         status = STATUS_PIPE_DISCONNECTED;
 
+    if ((status == STATUS_PENDING || status == STATUS_DEVICE_NOT_READY) && !async_queued( &sock->write_q ))
+    {
+        /* If write_q is not empty, we cannot really tell if the already queued
+         * asyncs will not consume all available space; if there's no space
+         * available, the current request won't be immediately satiable.
+         */
+        struct pollfd pollfd;
+        pollfd.fd = get_unix_fd( sock->fd );
+        pollfd.events = POLLOUT;
+        pollfd.revents = 0;
+        if (poll(&pollfd, 1, 0) >= 0 && pollfd.revents)
+        {
+            /* Give the client opportunity to complete synchronously.
+             * If it turns out that the I/O request is not actually immediately satiable,
+             * the client may then choose to re-queue the async (with STATUS_PENDING). */
+            status = STATUS_ALERTED;
+        }
+    }
+
     if ((async = create_request_async( fd, get_fd_comp_flags( fd ), &req->async )))
     {
         struct send_req *send_req;
@@ -3548,7 +3567,7 @@ DECL_HANDLER(send_socket)
         if (timeout)
             async_set_timeout( async, timeout, STATUS_IO_TIMEOUT );
 
-        if (status == STATUS_PENDING)
+        if (status == STATUS_PENDING || status == STATUS_ALERTED)
         {
             queue_async( &sock->write_q, async );
             sock_reselect( sock );
@@ -3556,6 +3575,7 @@ DECL_HANDLER(send_socket)
 
         reply->wait = async_handoff( async, NULL, 0 );
         reply->options = get_fd_options( fd );
+        reply->nonblocking = sock->nonblocking;
         release_object( async );
     }
     release_object( sock );
diff --git a/server/trace.c b/server/trace.c
index 75bc35b6b56..8653755e8a6 100644
--- a/server/trace.c
+++ b/server/trace.c
@@ -2053,6 +2053,7 @@ static void dump_send_socket_reply( const struct send_socket_reply *req )
 {
     fprintf( stderr, " wait=%04x", req->wait );
     fprintf( stderr, ", options=%08x", req->options );
+    fprintf( stderr, ", nonblocking=%d", req->nonblocking );
 }
 
 static void dump_get_next_console_request_request( const struct get_next_console_request_request *req )