feat: support for client Done in TxSubmission

protocol/txsubmission/client.go

@@ -124,7 +124,17 @@ func (c *Client) handleRequestTxIds(msg protocol.Message) error {
 		msgRequestTxIds.Req,
 	)
 	if err != nil {
-		return err
+		if !errors.Is(err, ErrStopServerProcess) {
+			return err
+		}
+		if !msgRequestTxIds.Blocking {
+			return errors.New("cannot stop server process during a non-blocking operation")
+		}
+		resp := NewMsgDone()
+		if err := c.SendMessage(resp); err != nil {
+			return err
+		}
+		return nil
 	}
 	resp := NewMsgReplyTxIds(txIds)
 	if err := c.SendMessage(resp); err != nil {

protocol/txsubmission/error.go

@@ -0,0 +1,21 @@
+// Copyright 2025 Blink Labs Software
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package txsubmission
+
+import "errors"
+
+// ErrStopServerProcess is used as a special return value from a RequestTxIds handler function to signify
+// that the server should stop asking for transactions. This should only be used when the request is blocking
+var ErrStopServerProcess = errors.New("stop server process")