Verifie aussi que tu ais fais ton bind sur toutes les interfaces et pas juste sur le localhost.
C'est a dire:
(c):
SOCKET sock;
SOCKADDR_IN sin;
sin.sin_addr.s_addr = htonl(INADDR_ANY);
sin.sin_family = AF_INET;
sin.sin_port = htons(50000);
sock = socket(AF_INET,SOCK_STREAM,0);
bind(sock, (SOCKADDR *)&sin, sizeof(sin));
et pas ca
(c):
SOCKET sock;
SOCKADDR_IN sin;
sin.sin_addr.s_addr = inet_addr("127.0.0.1");
sin.sin_family = AF_INET;
sin.sin_port = htons(50000);
sock = socket(AF_INET,SOCK_STREAM,0);
bind(sock, (SOCKADDR *)&sin, sizeof(sin));