diff --git a/include/hamlib/rig.h b/include/hamlib/rig.h
index 62575eed7..359ea3d32 100644
--- a/include/hamlib/rig.h
+++ b/include/hamlib/rig.h
@@ -211,12 +211,14 @@ typedef struct s_rig RIG;
 #define HAMLIB_MAX_SPECTRUM_MODES 5 /* max number of spectrum modes supported */
 #define HAMLIB_MAX_SPECTRUM_AVG_MODES 12 /* max number of spectrum averaging modes supported */
 #define HAMLIB_MAX_SPECTRUM_SPANS 20 /* max number of spectrum modes supported */
+#define HAMLIB_MAX_SPECTRUM_DATA 2048 /* max number of data bytes in a single spectrum line */
 #define HAMLIB_MAX_CAL_LENGTH 32   /* max calibration plots in cal_table_t */
 #define HAMLIB_MAX_MODES 63
 #define HAMLIB_MAX_VFOS 31
 #define HAMLIB_MAX_ROTORS 63
 #define HAMLIB_MAX_VFO_OPS 31
 #define HAMLIB_MAX_RSCANS 31
+#define HAMLIB_MAX_SNAPSHOT_PACKET_SIZE 16384 /* maximum number of bytes in a UDP snapshot packet */
 //! @endcond
 
 
diff --git a/src/event.c b/src/event.c
index e3183acef..eab14978f 100644
--- a/src/event.c
+++ b/src/event.c
@@ -751,11 +751,11 @@ int rig_fire_spectrum_event(RIG *rig, struct rig_spectrum_line *line)
 {
     ENTERFUNC;
 
-    if (rig_need_debug(RIG_DEBUG_ERR))
+    if (rig_need_debug(RIG_DEBUG_TRACE))
     {
         char spectrum_debug[line->spectrum_data_length * 4];
         print_spectrum_line(spectrum_debug, sizeof(spectrum_debug), line);
-        rig_debug(RIG_DEBUG_ERR, "%s: ASCII Spectrum Scope: %s\n", __func__,
+        rig_debug(RIG_DEBUG_TRACE, "%s: ASCII Spectrum Scope: %s\n", __func__,
                 spectrum_debug);
     }
 
diff --git a/src/iofunc.c b/src/iofunc.c
index c6f14e137..e8d2ad1a1 100644
--- a/src/iofunc.c
+++ b/src/iofunc.c
@@ -310,26 +310,26 @@ extern int is_uh_radio_fd(int fd);
 /* On MinGW32/MSVC/.. the appropriate accessor must be used
  * depending on the port type, sigh.
  */
-static ssize_t port_read(hamlib_port_t *p, void *buf, size_t count)
+static ssize_t port_read_generic(hamlib_port_t *p, void *buf, size_t count, int direct)
 {
+    int fd = direct ? p->fd : p->fd_sync_read;
     int i;
     ssize_t ret;
 
-    //ENTERFUNC; // too verbose
     /*
      * Since WIN32 does its special serial read, we have
      * to catch the microHam case to do just "read".
      * Note that we always have RIG_PORT_SERIAL in the
      * microHam case.
      */
-    if (is_uh_radio_fd(p->fd))
+    if (direct && is_uh_radio_fd(fd))
     {
-        return read(p->fd, buf, count);
+        return read(fd, buf, count);
     }
 
-    if (p->type.rig == RIG_PORT_SERIAL)
+    if (direct && p->type.rig == RIG_PORT_SERIAL)
     {
-        ret = win32_serial_read(p->fd, buf, count);
+        ret = win32_serial_read(fd, buf, (int) count);
 
         if (p->parm.serial.data_bits == 7)
         {
@@ -342,17 +342,15 @@ static ssize_t port_read(hamlib_port_t *p, void *buf, size_t count)
             }
         }
 
-        //RETURNFUNC(ret); // too verbose
         return ret;
     }
-    else if (p->type.rig == RIG_PORT_NETWORK
-             || p->type.rig == RIG_PORT_UDP_NETWORK)
+    else if (direct && (p->type.rig == RIG_PORT_NETWORK || p->type.rig == RIG_PORT_UDP_NETWORK))
     {
-        return recv(p->fd, buf, count, 0);
+        return recv(fd, buf, count, 0);
     }
     else
     {
-        return read(p->fd, buf, count);
+        return read(fd, buf, count);
     }
 }
 
@@ -371,7 +369,7 @@ static ssize_t port_write(hamlib_port_t *p, const void *buf, size_t count)
 
     if (p->type.rig == RIG_PORT_SERIAL)
     {
-        return win32_serial_write(p->fd, buf, count);
+        return win32_serial_write(p->fd, buf, (int) count);
     }
     else if (p->type.rig == RIG_PORT_NETWORK
              || p->type.rig == RIG_PORT_UDP_NETWORK)
@@ -390,7 +388,8 @@ static int port_select(hamlib_port_t *p,
                        fd_set *readfds,
                        fd_set *writefds,
                        fd_set *exceptfds,
-                       struct timeval *timeout)
+                       struct timeval *timeout,
+                       int direct)
 {
 #if 1
 
@@ -417,12 +416,12 @@ static int port_select(hamlib_port_t *p,
      * Note that we always have RIG_PORT_SERIAL in the
      * microHam case.
      */
-    if (is_uh_radio_fd(p->fd))
+    if (direct && is_uh_radio_fd(p->fd))
     {
         return select(n, readfds, writefds, exceptfds, timeout);
     }
 
-    if (p->type.rig == RIG_PORT_SERIAL)
+    if (direct && p->type.rig == RIG_PORT_SERIAL)
     {
         return win32_serial_select(n, readfds, writefds, exceptfds, timeout);
     }
@@ -465,7 +464,7 @@ static ssize_t port_read_generic(hamlib_port_t *p, void *buf, size_t count, int
 
 //! @cond Doxygen_Suppress
 #define port_write(p,b,c) write((p)->fd,(b),(c))
-#define port_select(p,n,r,w,e,t) select((n),(r),(w),(e),(t))
+#define port_select(p,n,r,w,e,t,d) select((n),(r),(w),(e),(t))
 //! @endcond
 
 #endif
@@ -503,8 +502,6 @@ int HAMLIB_API write_block(hamlib_port_t *p, const unsigned char *txbuffer, size
 {
     int ret;
 
-    //rig_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
-
 #ifdef WANT_NON_ACTIVE_POST_WRITE_DELAY
 
     if (p->post_write_date.tv_sec != 0)
@@ -599,14 +596,22 @@ int HAMLIB_API write_block(hamlib_port_t *p, const unsigned char *txbuffer, size
 
 int HAMLIB_API write_block_sync(hamlib_port_t *p, const unsigned char *txbuffer, size_t count)
 {
-    // TODO: Macro for write()
-    return (int) write((p)->fd_sync_write, txbuffer, count);
+    if (!p->async)
+    {
+        return -RIG_EINTERNAL;
+    }
+
+    return (int) write(p->fd_sync_write, txbuffer, count);
 }
 
 int HAMLIB_API write_block_sync_error(hamlib_port_t *p, const unsigned char *txbuffer, size_t count)
 {
-    // TODO: Macro for write()
-    return (int) write((p)->fd_sync_error_write, txbuffer, count);
+    if (!p->async)
+    {
+        return -RIG_EINTERNAL;
+    }
+
+    return (int) write(p->fd_sync_error_write, txbuffer, count);
 }
 
 static int read_block_generic(hamlib_port_t *p, unsigned char *rxbuffer, size_t count, int direct)
@@ -618,6 +623,11 @@ static int read_block_generic(hamlib_port_t *p, unsigned char *rxbuffer, size_t
 
     rig_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
 
+    if (!p->async && !direct)
+    {
+        return -RIG_EINTERNAL;
+    }
+
     fd = direct ? p->fd : p->fd_sync_read;
 
     /*
@@ -639,7 +649,7 @@ static int read_block_generic(hamlib_port_t *p, unsigned char *rxbuffer, size_t
         FD_SET(fd, &rfds);
         efds = rfds;
 
-        retval = port_select(p, fd + 1, &rfds, NULL, &efds, &tv);
+        retval = port_select(p, fd + 1, &rfds, NULL, &efds, &tv, direct);
 
         if (retval == 0)
         {
@@ -753,7 +763,7 @@ int HAMLIB_API read_block_direct(hamlib_port_t *p, unsigned char *rxbuffer, size
     return read_block_generic(p, rxbuffer, count, 1);
 }
 
-static int flush_and_read_last_byte(int fd)
+static int flush_and_read_last_byte(hamlib_port_t *p, int fd, int direct)
 {
     fd_set rfds, efds;
     ssize_t bytes_read;
@@ -769,7 +779,7 @@ static int flush_and_read_last_byte(int fd)
         FD_SET(fd, &rfds);
         efds = rfds;
 
-        retval = port_select(p, fd + 1, &rfds, NULL, &efds, &tv_timeout);
+        retval = port_select(p, fd + 1, &rfds, NULL, &efds, &tv_timeout, direct);
         if (retval < 0)
         {
             return -RIG_ETIMEOUT;
@@ -804,6 +814,11 @@ static int read_string_generic(hamlib_port_t *p,
     int total_count = 0;
     int i = 0;
 
+    if (!p->async && !direct)
+    {
+        return -RIG_EINTERNAL;
+    }
+
     rig_debug(RIG_DEBUG_TRACE, "%s called, rxmax=%d\n", __func__, (int)rxmax);
 
     if (!p || !rxbuffer)
@@ -849,7 +864,7 @@ static int read_string_generic(hamlib_port_t *p,
         }
         efds = rfds;
 
-        retval = port_select(p, maxfd + 1, &rfds, NULL, &efds, &tv);
+        retval = port_select(p, maxfd + 1, &rfds, NULL, &efds, &tv, direct);
 
         if (retval == 0)
         {
@@ -915,7 +930,7 @@ static int read_string_generic(hamlib_port_t *p,
 
             if (FD_ISSET(errorfd, &rfds))
             {
-                return flush_and_read_last_byte(errorfd);
+                return flush_and_read_last_byte(p, errorfd, 0);
             }
         }
 
diff --git a/src/network.c b/src/network.c
index 9b5c4a5cc..cc9a4ac97 100644
--- a/src/network.c
+++ b/src/network.c
@@ -658,12 +658,13 @@ static int multicast_publisher_read_packet(int fd, uint8_t *type, struct rig_spe
 
 void *multicast_publisher(void *arg)
 {
+    unsigned char spectrum_data[HAMLIB_MAX_SPECTRUM_DATA];
+    char snapshot_buffer[HAMLIB_MAX_SNAPSHOT_PACKET_SIZE];
+
     struct multicast_publisher_args_s *args = (struct multicast_publisher_args_s *)arg;
     RIG *rig = args->rig;
     struct rig_state *rs = &rig->state;
     struct rig_spectrum_line spectrum_line;
-    unsigned char spectrum_data[2048];
-    char snapshot_buffer[16 * 1024];
     uint8_t packet_type;
 
     struct sockaddr_in dest_addr;
diff --git a/src/rig.c b/src/rig.c
index 1bb6885bb..fa563857b 100644
--- a/src/rig.c
+++ b/src/rig.c
@@ -6376,7 +6376,7 @@ int HAMLIB_API rig_get_rig_info(RIG *rig, char *response, int max_response_len)
 
     if (ret != RIG_OK) { RETURNFUNC(ret); }
 
-    // we need both vfo and mode targtable to avoid vfo swapping
+    // we need both vfo and mode targetable to avoid vfo swapping
     if ((rig->caps->targetable_vfo & RIG_TARGETABLE_FREQ)
             && (rig->caps->targetable_vfo & RIG_TARGETABLE_MODE))
     {
diff --git a/src/snapshot_data.c b/src/snapshot_data.c
index 71876778a..baba1d1d9 100644
--- a/src/snapshot_data.c
+++ b/src/snapshot_data.c
@@ -9,14 +9,65 @@
 
 #include "cJSON.h"
 
-// Maximum number of data bytes in a single spectrum line
-#define SPECTRUM_DATA_MAX_LENGTH 2048
-
 #define MAX_VFO_COUNT 4
 
 #define SPECTRUM_MODE_FIXED "FIXED"
 #define SPECTRUM_MODE_CENTER "CENTER"
 
+static int snapshot_serialize_rig(cJSON *rig_node, RIG *rig)
+{
+    cJSON *node;
+
+    // TODO: need to assign rig an ID, e.g. from command line
+    node = cJSON_AddStringToObject(rig_node, "id", "rig_id");
+    if (node == NULL)
+    {
+        goto error;
+    }
+
+    // TODO: what kind of status should this reflect?
+    node = cJSON_AddStringToObject(rig_node, "status", rig->state.comm_state ? "OK" : "CLOSED");
+    if (node == NULL)
+    {
+        goto error;
+    }
+    // TODO: need to store last error code
+    node = cJSON_AddStringToObject(rig_node, "errorMsg", "");
+    if (node == NULL)
+    {
+        goto error;
+    }
+
+    node = cJSON_AddStringToObject(rig_node, "name", rig->caps->model_name);
+    if (node == NULL)
+    {
+        goto error;
+    }
+
+    node = cJSON_AddBoolToObject(rig_node, "split", rig->state.cache.split == RIG_SPLIT_ON ? 1 : 0);
+    if (node == NULL)
+    {
+        goto error;
+    }
+
+    node = cJSON_AddStringToObject(rig_node, "splitVfo", rig_strvfo(rig->state.cache.split_vfo));
+    if (node == NULL)
+    {
+        goto error;
+    }
+
+    node = cJSON_AddBoolToObject(rig_node, "satMode", rig->state.cache.satmode ? 1 : 0);
+    if (node == NULL)
+    {
+        goto error;
+    }
+
+    RETURNFUNC(RIG_OK);
+
+    error:
+    RETURNFUNC(-RIG_EINTERNAL);
+}
+
 static int snapshot_serialize_vfo(cJSON *vfo_node, RIG *rig, vfo_t vfo)
 {
     freq_t freq;
@@ -91,7 +142,7 @@ static int snapshot_serialize_vfo(cJSON *vfo_node, RIG *rig, vfo_t vfo)
 static int snapshot_serialize_spectrum(cJSON *spectrum_node, RIG *rig, struct rig_spectrum_line *spectrum_line)
 {
     // Spectrum data is represented as a hexadecimal ASCII string where each data byte is represented as 2 ASCII letters
-    char spectrum_data_string[SPECTRUM_DATA_MAX_LENGTH * 2];
+    char spectrum_data_string[HAMLIB_MAX_SPECTRUM_DATA * 2];
     cJSON *node;
     int i;
     struct rig_spectrum_scope *scopes = rig->caps->spectrum_scopes;
@@ -243,49 +294,15 @@ int snapshot_serialize(size_t buffer_length, char *buffer, RIG *rig, struct rig_
         goto error;
     }
 
+    result = snapshot_serialize_rig(rig_node, rig);
+    if (result != RIG_OK)
+    {
+        cJSON_Delete(rig_node);
+        goto error;
+    }
+
     cJSON_AddItemToObject(root_node, "rig", rig_node);
 
-    node = cJSON_AddStringToObject(rig_node, "id", "rig_id");
-    if (node == NULL)
-    {
-        goto error;
-    }
-
-    node = cJSON_AddStringToObject(rig_node, "status", "");
-    if (node == NULL)
-    {
-        goto error;
-    }
-    node = cJSON_AddStringToObject(rig_node, "errorMsg", "");
-    if (node == NULL)
-    {
-        goto error;
-    }
-
-    node = cJSON_AddStringToObject(rig_node, "name", rig->caps->model_name);
-    if (node == NULL)
-    {
-        goto error;
-    }
-
-    node = cJSON_AddBoolToObject(rig_node, "split", rig->state.cache.split == RIG_SPLIT_ON ? 1 : 0);
-    if (node == NULL)
-    {
-        goto error;
-    }
-
-    node = cJSON_AddStringToObject(rig_node, "splitVfo", rig_strvfo(rig->state.cache.split_vfo));
-    if (node == NULL)
-    {
-        goto error;
-    }
-
-    node = cJSON_AddBoolToObject(rig_node, "satMode", 0);
-    if (node == NULL)
-    {
-        goto error;
-    }
-
     vfos_array = cJSON_CreateArray();
     if (vfos_array == NULL)
     {