fix Bug: Disconnecting the gNB leads to an endless loop

src/sctp/sctp_server.cpp

@@ -158,7 +158,7 @@ int sctp_server::sctp_read_from_socket(int sd, uint32_t ppid) {
   int n = sctp_recvmsg(
       sd, (void*) buffer, SCTP_RECV_BUFFER_SIZE, (struct sockaddr*) &addr,
       &from_len, &sinfo, &flags);
-  if (n < 0) {
+  if (n <= 0) {
     Logger::sctp().error("sctp_recvmsg error:: %s:%d", strerror(errno), errno);
     return SCTP_RC_ERROR;
   }
@@ -211,6 +211,7 @@ int sctp_server::sctp_read_from_socket(int sd, uint32_t ppid) {
 int sctp_server::sctp_handle_com_down(sctp_assoc_id_t assoc_id) {
   Logger::sctp().info("SCTP_SHUTDOWN_COMP assoc_id (%d) ", assoc_id);
   app_->handle_sctp_del_association(assoc_id);
+  return SCTP_RC_DISCONNECT;
 }
 
 //------------------------------------------------------------------------------