diff --git a/common/trans.c b/common/trans.c
index 9611f768..9e877d5c 100644
--- a/common/trans.c
+++ b/common/trans.c
@@ -28,7 +28,7 @@
 
 /*****************************************************************************/
 int APP_CC
-trans_tls_recv(struct trans *self, void *ptr, int len)
+trans_tls_recv(struct trans *self, char *ptr, int len)
 {
     if (self->tls == NULL)
     {
@@ -39,7 +39,7 @@ trans_tls_recv(struct trans *self, void *ptr, int len)
 
 /*****************************************************************************/
 int APP_CC
-trans_tls_send(struct trans *self, const void *data, int len)
+trans_tls_send(struct trans *self, const char *data, int len)
 {
     if (self->tls == NULL)
     {
@@ -61,14 +61,14 @@ trans_tls_can_recv(struct trans *self, int sck, int millis)
 
 /*****************************************************************************/
 int APP_CC
-trans_tcp_recv(struct trans *self, void *ptr, int len)
+trans_tcp_recv(struct trans *self, char *ptr, int len)
 {
     return g_tcp_recv(self->sck, ptr, len, 0);
 }
 
 /*****************************************************************************/
 int APP_CC
-trans_tcp_send(struct trans *self, const void *data, int len)
+trans_tcp_send(struct trans *self, const char *data, int len)
 {
     return g_tcp_send(self->sck, data, len, 0);
 }
diff --git a/common/trans.h b/common/trans.h
index 639e64d1..1bb15bcf 100644
--- a/common/trans.h
+++ b/common/trans.h
@@ -41,8 +41,8 @@ typedef int (DEFAULT_CC *ttrans_data_in)(struct trans* self);
 typedef int (DEFAULT_CC *ttrans_conn_in)(struct trans* self,
                                          struct trans* new_self);
 typedef int (DEFAULT_CC *tis_term)(void);
-typedef int (APP_CC *trans_recv_proc) (struct trans *self, void *ptr, int len);
-typedef int (APP_CC *trans_send_proc) (struct trans *self, const void *data, int len);
+typedef int (APP_CC *trans_recv_proc) (struct trans *self, char *ptr, int len);
+typedef int (APP_CC *trans_send_proc) (struct trans *self, const char *data, int len);
 typedef int (APP_CC *trans_can_recv_proc) (struct trans *self, int sck, int millis);
 
 /* optional source info */