diff --git a/.gitmodules b/.gitmodules
index f7712e2..016547a 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -13,3 +13,9 @@
 [submodule "src/c++/deps/opendnp3"]
 	path = src/c++/deps/opendnp3
 	url = https://github.com/dnp3/opendnp3.git
+[submodule "src/c/deps/json-c"]
+	path = src/c/deps/json-c
+	url = https://github.com/json-c/json-c.git
+[submodule "src/c/deps/libiec61850"]
+	path = src/c/deps/libiec61850
+	url = https://github.com/mz-automation/libiec61850.git
diff --git a/Dockerfile b/Dockerfile
index 09073aa..2acea34 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -44,6 +44,10 @@ ADD CMakeLists.txt /usr/local/src/ot-sim/CMakeLists.txt
 ADD src/c          /usr/local/src/ot-sim/src/c
 ADD src/c++        /usr/local/src/ot-sim/src/c++
 RUN cmake -S /usr/local/src/ot-sim -B /usr/local/src/ot-sim/build \
+  && cmake -S /usr/local/src/ot-sim/src/c/deps/json-c -B /usr/local/src/ot-sim/src/c/deps/json-c/build \
+  && cmake --build /usr/local/src/ot-sim/src/c/deps/json-c/build -j $(nproc) --target install
+  && cmake -S /usr/local/src/ot-sim/src/c/deps/libiec61850 -B /usr/local/src/ot-sim/src/c/deps/libiec61850/build \
+  && cmake --build /usr/local/src/ot-sim/src/c/deps/libiec61850/build -j $(nproc) --target install
   && cmake --build /usr/local/src/ot-sim/build -j $(nproc) --target install
 
 FROM debian:bookworm AS prod
diff --git a/src/c/CMakeLists.txt b/src/c/CMakeLists.txt
index 978460f..a220ca2 100644
--- a/src/c/CMakeLists.txt
+++ b/src/c/CMakeLists.txt
@@ -1 +1,8 @@
+set(JSON_INCLUDE_DIRS
+  ${CMAKE_SOURCE_DIR}/deps
+)
+
+add_subdirectory(deps/json-c)
+
+add_subdirectory(cmd/ot-sim-61850-module)
 add_subdirectory(cmd/ot-sim-message-bus)
diff --git a/src/c/cmd/ot-sim-61850-module/CMakeLists.txt b/src/c/cmd/ot-sim-61850-module/CMakeLists.txt
new file mode 100644
index 0000000..07e9f0c
--- /dev/null
+++ b/src/c/cmd/ot-sim-61850-module/CMakeLists.txt
@@ -0,0 +1,22 @@
+find_package(LibXml2 REQUIRED)
+
+include_directories(
+  ${JSON_INCLUDE_DIRS}
+  ${LIBXML2_INCLUDE_DIR}
+)
+
+add_executable(ot-sim-61850-module
+  main.c
+)
+
+target_link_libraries(ot-sim-61850-module
+  czmq
+  ${LIBXML2_LIBRARIES}
+  json-c
+  pthread
+  zmq
+)
+
+install(TARGETS ot-sim-61850-module
+  RUNTIME DESTINATION bin
+)
diff --git a/src/c/cmd/ot-sim-61850-module/main.c b/src/c/cmd/ot-sim-61850-module/main.c
new file mode 100644
index 0000000..a561259
--- /dev/null
+++ b/src/c/cmd/ot-sim-61850-module/main.c
@@ -0,0 +1,490 @@
+#include <errno.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <czmq.h>
+#include <json-c/json.h>
+#include <libxml/parser.h>
+
+#include <libiec61850/iec61850_server.h>
+
+// ---- BEGIN PUB/SUB STUFF
+// ---- PUTTING THIS HERE SINCE HAVING IT IN A SEPARATE HEADER/SOURCE FILE
+// ---- CAUSES "MULTIPLE DEFINITION" ERRORS WITH HELICS CONSTANTS
+typedef struct _subscriptions {
+  const char **names;
+  const char **types;
+  const char **tags;
+
+  unsigned int size;
+} otsim_subscriptions_t;
+
+typedef struct _publications {
+  const char **names;
+  const char **types;
+  const char **tags;
+
+  double *values;
+  bool *updates;
+
+  unsigned int size;
+} otsim_publications_t;
+
+otsim_subscriptions_t *otsim_subscriptions_new(unsigned int size) {
+  otsim_subscriptions_t *subs;
+
+  subs = (otsim_subscriptions_t *)malloc(sizeof(otsim_subscriptions_t));
+  if (subs == NULL)
+    return NULL;
+
+  
+  subs->names = (const char **) malloc(size * sizeof(const char *));
+  subs->types = (const char **) malloc(size * sizeof(const char *));
+  subs->tags  = (const char **) calloc(size, sizeof(const char *));
+  subs->size  = size;
+
+  return subs;
+}
+
+void otsim_subscriptions_free(otsim_subscriptions_t *subs) {
+  free(subs->names);
+  free(subs->types);
+  free(subs->tags);
+}
+
+otsim_publications_t *otsim_publications_new(unsigned int size) {
+  otsim_publications_t *pubs;
+
+  pubs = (otsim_publications_t *)malloc(sizeof(otsim_publications_t));
+  if (pubs == NULL)
+    return NULL;
+
+  
+  pubs->names   = (const char **) malloc(size * sizeof(const char *));
+  pubs->types   = (const char **) malloc(size * sizeof(const char *));
+  pubs->tags    = (const char **) calloc(size, sizeof(const char *));
+  pubs->values  = (double *)      malloc(size * sizeof(double));
+  pubs->updates = (bool *)        calloc(size, sizeof(bool));
+  pubs->size    = size;
+
+  return pubs;
+}
+
+void otsim_publications_free(otsim_publications_t *pubs) {
+  free(pubs->names);
+  free(pubs->types);
+  free(pubs->tags);
+  free(pubs->values);
+  free(pubs->updates);
+}
+// ---- END PUB/SUB STUFF
+
+static otsim_subscriptions_t *subs;
+static otsim_publications_t *pubs;
+
+static zsock_t *pusher;
+static zsock_t *subscriber;
+static zpoller_t *poller;
+
+static int running;
+
+static void trap(int sig) {
+  running = 0; // TODO: make this thread-safe?
+
+  otsim_subscriptions_free(subs);
+  otsim_publications_free(pubs);
+
+  zsock_destroy(&pusher);
+  zsock_destroy(&subscriber);
+  zpoller_destroy(&poller);
+
+  exit(sig);
+}
+
+typedef struct {
+  const char *pull;
+  const char *publish;
+  const char *broker;
+  const char *name;
+} config;
+
+#define MATCHXML(e, n) xmlStrcmp(e->name, (const xmlChar*) n) == 0
+
+// handle "subscriptions" element
+static int sub_handler(config *c, xmlDoc *doc, xmlNode *node) {
+  int count = xmlChildElementCount(node);
+  subs = otsim_subscriptions_new(count);
+
+  xmlNode *sub = node->xmlChildrenNode;
+  int idx = 0;
+
+  xmlChar *text;
+
+  while (sub != NULL) {
+    if (MATCHXML(sub, "subscription")) {
+      xmlNode *setting = sub->xmlChildrenNode;
+
+      while (setting != NULL) {
+        text = xmlNodeListGetString(doc, setting->xmlChildrenNode, 1);
+
+        if (MATCHXML(setting, "key")) {
+          subs->names[idx] = strdup(text);
+
+          if (subs->tags[idx] == NULL) {
+            subs->tags[idx] = strdup(text);
+          }
+        } else if (MATCHXML(setting, "type")) {
+          subs->types[idx] = strdup(text);
+        } else if (MATCHXML(setting, "tag")) {
+          subs->tags[idx] = strdup(text);
+        }
+
+        xmlFree(text);
+        setting = setting->next;
+      }
+
+      idx++;
+    }
+
+    sub = sub->next;
+  }
+
+  return 0;
+}
+
+// handle "publications" element
+static int pub_handler(config *c, xmlDoc *doc, xmlNode *node) {
+  int count = xmlChildElementCount(node);
+  pubs = otsim_publications_new(count);
+
+  xmlNode *pub = node->xmlChildrenNode;
+  int idx = 0;
+
+  xmlChar *text;
+
+  while (pub != NULL) {
+    if (MATCHXML(pub, "publication")) {
+      xmlNode *setting = pub->xmlChildrenNode;
+
+      while (setting != NULL) {
+        text = xmlNodeListGetString(doc, setting->xmlChildrenNode, 1);
+
+        if (MATCHXML(setting, "key")) {
+          pubs->names[idx] = strdup(text);
+
+          if (pubs->tags[idx] == NULL) {
+            pubs->tags[idx] = strdup(text);
+          }
+        } else if (MATCHXML(setting, "type")) {
+          pubs->types[idx] = strdup(text);
+        } else if (MATCHXML(setting, "tag")) {
+          pubs->tags[idx] = strdup(text);
+        }
+
+        xmlFree(text);
+        setting = setting->next;
+      }
+
+      idx++;
+    }
+
+    pub = pub->next;
+  }
+
+  return 0;
+}
+
+// handle "io" element
+static int xml_handler(config *c, xmlDoc *doc, xmlNode *node) {
+  xmlChar *text;
+
+  node = node->xmlChildrenNode;
+
+  while (node != NULL) {
+    text = xmlNodeListGetString(doc, node->xmlChildrenNode, 1);
+
+    if (MATCHXML(node, "pull-endpoint")) {
+      c->pull = strdup(text);
+    } else if (MATCHXML(node, "pub-endpoint")) {
+      c->publish = strdup(text);
+    } else if (MATCHXML(node, "broker-endpoint")) {
+      c->broker = strdup(text);
+    } else if (MATCHXML(node, "federate-name")) {
+      c->name = strdup(text);
+    } else if (MATCHXML(node, "subscriptions")) {
+      int rc = sub_handler(c, doc, node);
+      if (rc != 0) {
+        return rc;
+      }
+    } else if (MATCHXML(node, "publications")) {
+      int rc = pub_handler(c, doc, node);
+      if (rc != 0) {
+        return rc;
+      }
+    }
+
+    xmlFree(text);
+    node = node->next;
+  }
+
+  return 0;
+}
+
+static int xml_parse(char *path, config *c) {
+  xmlDoc *doc;
+  xmlNode *node;
+
+  doc = xmlParseFile(path);
+
+  if (doc == NULL) {
+    return -1;
+  }
+
+  node = xmlDocGetRootElement(doc);
+
+  if (node == NULL) {
+    xmlFreeDoc(doc);
+    return -1;
+  }
+
+  if (!MATCHXML(node, "ot-sim")) {
+    xmlFreeDoc(doc);
+    return -1;
+  }
+
+  node = node->xmlChildrenNode;
+
+  while (node != NULL) {
+    // look for top-level io element only
+    if (MATCHXML(node, "iec-61850")) {
+      int rc = xml_handler(c, doc, node);
+
+      xmlFreeDoc(doc);
+      return rc;
+    }
+
+    node = node->next;
+  }
+
+  xmlFreeDoc(doc);
+  return 0;
+}
+
+typedef struct {
+  const char *tag;
+  double     value;
+  uint64_t   ts;
+} point_t;
+
+typedef struct {
+  point_t    *updates;
+  const char *recipient;
+  const char *confirm;
+
+  unsigned int size;
+} update_t;
+
+typedef struct {
+  const char *api_version;
+  const char *kind;
+
+  struct {
+    const char *sender;
+  } metadata;
+
+  json_object *contents;
+} envelope_t;
+
+void update_free(update_t *update) {
+  free(update->updates);
+}
+
+static int envelope_marshal(envelope_t env, json_object *root) {
+  json_object *md_obj = json_object_new_object();
+
+  json_object_object_add(root, "apiVersion", json_object_new_string("v1"));
+  json_object_object_add(root, "kind", json_object_new_string(env.kind));
+  json_object_object_add(root, "metadata", md_obj);
+
+  json_object_object_add(md_obj, "sender", json_object_new_string(env.metadata.sender));
+
+  return 0;
+}
+
+static int envelope_add_measurements(json_object *root, int len, point_t *points) {
+  json_object *contents_obj     = json_object_new_object();
+  json_object *measurements_arr = json_object_new_array_ext(len);
+
+  for (int i = 0; i < len; i++) {
+    json_object *point_obj = json_object_new_object();
+
+    json_object_object_add(point_obj, "tag",   json_object_new_string(points[i].tag));
+    json_object_object_add(point_obj, "value", json_object_new_double(points[i].value));
+    json_object_object_add(point_obj, "ts",    json_object_new_uint64(points[i].ts));
+
+    json_object_array_add(measurements_arr, point_obj);
+  }
+
+  json_object_object_add(contents_obj, "measurements", measurements_arr);
+  json_object_object_add(root, "contents", contents_obj);
+
+  return 0;
+}
+
+static int envelope_unmarshal(char *data, json_object *root, envelope_t *env) {
+  root = json_tokener_parse(data);
+
+  json_object *version_obj  = json_object_object_get(root, "apiVersion");
+  json_object *kind_obj     = json_object_object_get(root, "kind");
+  json_object *md_obj       = json_object_object_get(root, "metadata");
+  json_object *contents_obj = json_object_object_get(root, "contents");
+
+  json_object *sender_obj = json_object_object_get(md_obj, "sender");
+
+  env->api_version     = json_object_get_string(version_obj);
+  env->kind            = json_object_get_string(kind_obj);
+  env->metadata.sender = json_object_get_string(sender_obj);
+
+  env->contents = contents_obj;
+
+  return 0;
+}
+
+static int *update_unmarshal(json_object *root, update_t *update) {
+  json_object *updates   = json_object_object_get(root, "updates");
+  json_object *recipient = json_object_object_get(root, "recipient");
+  json_object *confirm   = json_object_object_get(root, "confirm");
+
+  if (recipient != NULL) {
+    update->recipient = json_object_get_string(recipient);
+  }
+
+  if (confirm != NULL) {
+    update->confirm   = json_object_get_string(confirm);
+  }
+
+  int len = json_object_array_length(updates);
+
+  update->size    = len;
+  update->updates = (point_t*) malloc(len * sizeof(point_t));
+
+  for (int i = 0; i < len; i++) {
+    json_object *el    = json_object_array_get_idx(updates, i);
+    json_object *tag   = json_object_object_get(el, "tag");
+    json_object *value = json_object_object_get(el, "value");
+
+    point_t point = {
+      .tag   = json_object_get_string(tag),
+      .value = json_object_get_double(value),
+    };
+
+    update->updates[i] = point;
+  }
+
+  return 0;
+}
+
+int main(int argc, char **argv) {
+  config c;
+
+  c.pull    = "tcp://127.0.0.1:1234";
+  c.publish = "tcp://127.0.0.1:5678";
+  c.name    = "IEC-61850";
+
+  if (argc == 2) {
+    printf("loading config %s\n", argv[1]);
+
+    if (xml_parse(argv[1], &c) != 0) {
+      puts("cannot load XML config");
+      return 1;
+    }
+  }
+
+  pusher = zsock_new_push(c.pull);
+  subscriber = zsock_new_sub(c.publish, "RUNTIME");
+  poller = zpoller_new(subscriber, NULL);
+
+  // Initialize subs so for loops below don't error out.
+  if (subs == NULL) {
+    subs = otsim_subscriptions_new(0);
+  }
+
+  // Initialize pubs so for loops below don't error out.
+  if (pubs == NULL) {
+    pubs = otsim_publications_new(0);
+  }
+
+  signal(SIGINT, trap);
+  running = 1;
+
+  IedServerConfig config = IedServerConfig_create();
+
+  DataObject iedModel_GenericIO_GGIO1_SPCSO1 = {
+    DataObjectModelType,
+    "SPCSO1",
+    (ModelNode*) &iedModel_GenericIO_GGIO1,
+    (ModelNode*) &iedModel_GenericIO_GGIO1_SPCSO2,
+    (ModelNode*) &iedModel_GenericIO_GGIO1_SPCSO1_origin,
+    0
+};
+
+  while (running) {
+    // Use poller here so we can break out of this thread quickly if program is
+    // canceled.
+    zsock_t *sock = (zsock_t*) zpoller_wait(poller, 5000);
+
+    if (sock == subscriber) {
+      char *filter;
+      char *data;
+
+      if (zstr_recvx(sock, &filter, &data, NULL) != 2) {
+        printf("[I/O] expected more messages\n");
+        continue;
+      }
+
+      json_object *root;
+      envelope_t env;
+
+      envelope_unmarshal(data, root, &env);
+
+      if (strcmp(c.name, env.metadata.sender) == 0) {
+        continue;
+      }
+
+      if (strcmp("Update", env.kind) != 0) {
+        continue;
+      }
+
+      update_t update;
+
+      update_unmarshal(env.contents, &update);
+
+      if (strlen(update.recipient) > 0 && strcmp(c.name, update.recipient) != 0) {
+        continue;
+      }
+
+      for (int i = 0; i < pubs->size; i++) {
+        const char *tag = pubs->tags[i];
+
+        for (int j = 0; j < update.size; j++) {
+          point_t point = update.updates[j];
+
+          if (strcmp(tag, point.tag) == 0) {
+            printf("updating publication %s to %f\n", pubs->names[i], point.value);
+
+            pubs->values[i] = point.value;
+            pubs->updates[i] = true;
+
+            break;
+          }
+        }
+      }
+
+      update_free(&update);
+      json_object_put(root);
+    }
+  }
+}
\ No newline at end of file
diff --git a/src/c/deps/json-c b/src/c/deps/json-c
new file mode 160000
index 0000000..e3464a2
--- /dev/null
+++ b/src/c/deps/json-c
@@ -0,0 +1 @@
+Subproject commit e3464a2ab4e0a7166543a178cb9f26c4cb3b9b61
diff --git a/src/c/deps/libiec61850 b/src/c/deps/libiec61850
new file mode 160000
index 0000000..7afa403
--- /dev/null
+++ b/src/c/deps/libiec61850
@@ -0,0 +1 @@
+Subproject commit 7afa40390b26ad1f4cf93deaa0052fe7e357ef33