diff --git a/include/libssh2.h b/include/libssh2.h
index 6440001..3e4c01f 100644
--- a/include/libssh2.h
+++ b/include/libssh2.h
@@ -166,6 +166,15 @@ typedef long long libssh2_int64_t;
                                               void **abstract)
 #define LIBSSH2_FREE_FUNC(name)    void name(void *ptr, void **abstract)
 
+/* custom i/o  callbacks */
+#define LIBSSH2_RECV_FUNC(name)  ssize_t name(int socket, \
+                                              void *buffer, size_t length, \
+                                              int flags, void **abstract);
+#define LIBSSH2_SEND_FUNC(name)  ssize_t name(int socket, \
+                                              const void *buffer, size_t length,\
+                                              int flags, void **abstract);
+
+
 typedef struct _LIBSSH2_USERAUTH_KBDINT_PROMPT
 {
     char* text;
@@ -228,6 +237,8 @@ typedef struct _LIBSSH2_USERAUTH_KBDINT_RESPONSE
 #define LIBSSH2_CALLBACK_DISCONNECT         2
 #define LIBSSH2_CALLBACK_MACERROR           3
 #define LIBSSH2_CALLBACK_X11                4
+#define LIBSSH2_CALLBACK_SEND               5
+#define LIBSSH2_CALLBACK_RECV               6
 
 /* libssh2_session_method_pref() constants */
 #define LIBSSH2_METHOD_KEX          0
diff --git a/src/libssh2_priv.h b/src/libssh2_priv.h
index c50fa8c..f2359f3 100644
--- a/src/libssh2_priv.h
+++ b/src/libssh2_priv.h
@@ -675,6 +675,8 @@ struct _LIBSSH2_SESSION
       LIBSSH2_DISCONNECT_FUNC((*ssh_msg_disconnect));
       LIBSSH2_MACERROR_FUNC((*macerror));
       LIBSSH2_X11_OPEN_FUNC((*x11));
+      LIBSSH2_SEND_FUNC((*send));
+      LIBSSH2_RECV_FUNC((*recv));
 
     /* Method preferences -- NULL yields "load order" */
     char *kex_prefs;
diff --git a/src/session.c b/src/session.c
index f6498e4..3c4b5a9 100644
--- a/src/session.c
+++ b/src/session.c
@@ -112,9 +112,15 @@ banner_receive(LIBSSH2_SESSION * session)
         /* no incoming block yet! */
         session->socket_block_directions &= ~LIBSSH2_SESSION_BLOCK_INBOUND;
 
-        ret = _libssh2_recv(session->socket_fd, &c, 1,
-                            LIBSSH2_SOCKET_RECV_FLAGS(session));
-        if (ret < 0)
+        if(session->recv){
+            ret = session->recv(session->socket_fd, &c, 1,
+                                LIBSSH2_SOCKET_RECV_FLAGS(session),
+                                &session->abstract);
+        }else{
+            ret = _libssh2_recv(session->socket_fd, &c, 1,
+                                LIBSSH2_SOCKET_RECV_FLAGS(session));
+        }
+        if (ret < 0 && (!session->recv || ret!=-EAGAIN))
             _libssh2_debug(session, LIBSSH2_TRACE_SOCKET,
                            "Error recving %d bytes to %p: %d", 1, &c, errno);
         else
@@ -122,7 +128,7 @@ banner_receive(LIBSSH2_SESSION * session)
                            "Recved %d bytes to %p", ret, &c);
 
         if (ret < 0) {
-            if (errno == EAGAIN) {
+            if (errno == EAGAIN || (session->recv && ret==-EAGAIN)) {
                 session->socket_block_directions =
                     LIBSSH2_SESSION_BLOCK_INBOUND;
                 session->banner_TxRx_total_send = banner_len;
@@ -221,11 +227,19 @@ banner_send(LIBSSH2_SESSION * session)
     /* no outgoing block yet! */
     session->socket_block_directions &= ~LIBSSH2_SESSION_BLOCK_OUTBOUND;
 
-    ret = _libssh2_send(session->socket_fd,
-                        banner + session->banner_TxRx_total_send,
-                        banner_len - session->banner_TxRx_total_send,
-                        LIBSSH2_SOCKET_SEND_FLAGS(session));
-    if (ret < 0)
+    if(session->send){
+        ret = session->send(session->socket_fd,
+                            banner + session->banner_TxRx_total_send,
+                            banner_len - session->banner_TxRx_total_send,
+                            LIBSSH2_SOCKET_SEND_FLAGS(session),
+                            &session->abstract);
+    }else{
+        ret = _libssh2_send(session->socket_fd,
+                            banner + session->banner_TxRx_total_send,
+                            banner_len - session->banner_TxRx_total_send,
+                            LIBSSH2_SOCKET_SEND_FLAGS(session));
+    }
+    if (ret < 0 && (!session->send || ret!=-EAGAIN))
         _libssh2_debug(session, LIBSSH2_TRACE_SOCKET,
                        "Error sending %d bytes: %d",
                        banner_len - session->banner_TxRx_total_send, errno);
@@ -236,7 +250,8 @@ banner_send(LIBSSH2_SESSION * session)
                        banner, session->banner_TxRx_total_send);
 
     if (ret != (banner_len - session->banner_TxRx_total_send)) {
-        if ((ret > 0) || ((ret == -1) && (errno == EAGAIN))) {
+        if ((ret > 0) || ((ret == -1) && (errno == EAGAIN)) ||
+            (session->send && ret==-EAGAIN)) {
             /* the whole packet could not be sent, save the what was */
             session->socket_block_directions =
                 LIBSSH2_SESSION_BLOCK_OUTBOUND;
@@ -525,6 +540,15 @@ libssh2_session_callback_set(LIBSSH2_SESSION * session,
         session->x11 = callback;
         return oldcb;
 
+    case LIBSSH2_CALLBACK_SEND:
+        oldcb = session->send;
+        session->send = callback;
+        return oldcb;
+
+    case LIBSSH2_CALLBACK_RECV:
+        oldcb = session->recv;
+        session->recv = callback;
+        return oldcb;
     }
     _libssh2_debug(session, LIBSSH2_TRACE_TRANS, "Setting Callback %d", cbtype);
 
diff --git a/src/transport.c b/src/transport.c
index 374c09b..4338066 100644
--- a/src/transport.c
+++ b/src/transport.c
@@ -372,10 +372,19 @@ int _libssh2_transport_read(LIBSSH2_SESSION * session)
             }
 
             /* now read a big chunk from the network into the temp buffer */
-            nread =
-                _libssh2_recv(session->socket_fd, &p->buf[remainbuf],
-                              PACKETBUFSIZE - remainbuf,
-                              LIBSSH2_SOCKET_RECV_FLAGS(session));
+            if(session->recv){
+                nread =
+                    session->recv(session->socket_fd, &p->buf[remainbuf],
+                                  PACKETBUFSIZE - remainbuf,
+                                  LIBSSH2_SOCKET_RECV_FLAGS(session),
+                                  &session->abstract);
+
+            }else {
+                nread =
+                    _libssh2_recv(session->socket_fd, &p->buf[remainbuf],
+                                  PACKETBUFSIZE - remainbuf,
+                                  LIBSSH2_SOCKET_RECV_FLAGS(session));
+            }
             if (nread < 0)
                 _libssh2_debug(session, LIBSSH2_TRACE_SOCKET,
                                "Error recving %d bytes to %p+%d: %d",
@@ -388,7 +397,8 @@ int _libssh2_transport_read(LIBSSH2_SESSION * session)
             if (nread <= 0) {
                 /* check if this is due to EAGAIN and return the special
                    return code if so, error out normally otherwise */
-                if ((nread < 0) && (errno == EAGAIN)) {
+                if (((nread < 0) && ((errno == EAGAIN)))
+                    || ( session->recv && nread== -EAGAIN )){
                     session->socket_block_directions |=
                         LIBSSH2_SESSION_BLOCK_INBOUND;
                     return LIBSSH2_ERROR_EAGAIN;
@@ -642,9 +652,14 @@ send_existing(LIBSSH2_SESSION * session, unsigned char *data,
     /* number of bytes left to send */
     length = p->ototal_num - p->osent;
 
-    rc = _libssh2_send(session->socket_fd, &p->outbuf[p->osent], length,
-                       LIBSSH2_SOCKET_SEND_FLAGS(session));
-    if (rc < 0)
+    if(session->send){
+        rc = session->send(session->socket_fd, &p->outbuf[p->osent], length,
+                           LIBSSH2_SOCKET_SEND_FLAGS(session),&session->abstract);
+    }else{
+        rc = _libssh2_send(session->socket_fd, &p->outbuf[p->osent], length,
+                           LIBSSH2_SOCKET_SEND_FLAGS(session));
+    }
+    if (rc < 0 && (!session->send || rc!=-EAGAIN))
         _libssh2_debug(session, LIBSSH2_TRACE_SOCKET,
                        "Error sending %d bytes: %d", length, errno);
     else
@@ -665,7 +680,7 @@ send_existing(LIBSSH2_SESSION * session, unsigned char *data,
     }
     else if (rc < 0) {
         /* nothing was sent */
-        if (errno != EAGAIN) {
+        if (errno != EAGAIN && ( !session->send || rc!=-EAGAIN )) {
             /* send failure! */
             return LIBSSH2_ERROR_SOCKET_NONE;
         }
@@ -824,9 +839,14 @@ _libssh2_transport_write(LIBSSH2_SESSION * session, unsigned char *data,
 
     session->local.seqno++;
 
-    ret = _libssh2_send(session->socket_fd, p->outbuf, total_length,
-                        LIBSSH2_SOCKET_SEND_FLAGS(session));
-    if (ret < 0)
+    if(session->send){
+        ret = session->send(session->socket_fd, p->outbuf, total_length,
+                            LIBSSH2_SOCKET_SEND_FLAGS(session),&session->abstract);
+    }else{
+        ret = _libssh2_send(session->socket_fd, p->outbuf, total_length,
+                            LIBSSH2_SOCKET_SEND_FLAGS(session));
+    }
+    if (ret < 0 && (!session->send || ret!=-EAGAIN))
         _libssh2_debug(session, LIBSSH2_TRACE_SOCKET,
                        "Error sending %d bytes: %d", total_length, errno);
     else
@@ -837,7 +857,8 @@ _libssh2_transport_write(LIBSSH2_SESSION * session, unsigned char *data,
         debugdump(session, "libssh2_transport_write send()", p->outbuf, ret);
     }
     if (ret != total_length) {
-        if ((ret > 0) || ((ret == -1) && (errno == EAGAIN))) {
+        if ((ret > 0) || ((ret == -1) && (errno == EAGAIN)) ||
+            (session->send && ret==-EAGAIN)) {
             /* the whole packet could not be sent, save the rest */
             session->socket_block_directions |= LIBSSH2_SESSION_BLOCK_OUTBOUND;
             p->odata = orgdata;