[Udpcast] Socket problem in receiver

Hello, I´m using latest udpcast versión (20100130) in Debian machines to transfer files in unidirectional mode. Sometimes I see the next message in receiver machine: “Receiver error” After putting some fprintf I realized the problem is in the file udpr-negotiate.c in line 191: sock = udpc_selectSock(client_config.socks, NR_CLIENT_SOCKS, net_config->startTimeout); if(sock < 0) { return -1; } Why sock is < 0? What should I do? Thanks