diff --git a/idl/mdsconnect.pro b/idl/mdsconnect.pro
index 77e5fea488..1b0398e13a 100644
--- a/idl/mdsconnect.pro
+++ b/idl/mdsconnect.pro
@@ -6,7 +6,8 @@ endcase
 end
 
 function sockmin
-  if !version.os eq 'linux' then return, 0 else return, 11-(!version.os eq 'MacOS')
+  ; Connection IDs start at 1 (see Issue #2625 for details).
+  if !version.os eq 'linux' then return, 1 else return, 11-(!version.os eq 'MacOS')
 end
 
 function mds$socket,quiet=quiet,status=status,socket=socket
diff --git a/mdstcpip/mdsipshr/Connections.c b/mdstcpip/mdsipshr/Connections.c
index 297614d235..90fe125436 100644
--- a/mdstcpip/mdsipshr/Connections.c
+++ b/mdstcpip/mdsipshr/Connections.c
@@ -465,13 +465,17 @@ static inline int authorize_client(Connection *c, char *username)
 int AddConnection(Connection *c)
 {
   MDSIPTHREADSTATIC_INIT;
+  
+  // Connection IDs are issued in sequence.
+  // Issue #2625 requires connection IDs starting at 1 to avoid IDL issues.
+  // Use of _FindConnection() is an integrity check of the data structures.
   static int id = INVALID_CONNECTION_ID;
   static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
   pthread_mutex_lock(&lock);
   do
   {
-    id++; // find next free id
-  } while (id == INVALID_CONNECTION_ID && _FindConnection(id, NULL, MDSIPTHREADSTATIC_VAR));
+    id++;
+  } while ((id == INVALID_CONNECTION_ID) || (id == 0) || _FindConnection(id, NULL, MDSIPTHREADSTATIC_VAR));
   c->id = id;
   pthread_mutex_unlock(&lock);
   c->state |= CON_INLIST;