C ++如何在Linux上的fork（）之后防止子进程绑定端口？

Question

I have a "launcher" programs that listens to port X, and then starts other processess with fork()

signal(SIGCHLD, SIG_IGN);
    a.sin_port=htons(atoi(argv[1]));
        if(bind(os,(struct sockaddr *)&a,sizeof(a)) == -1) {
            if(Debug){
            printf("Launher: Can't bind our address (%s)\n", argv[1]);
        }
            exit(1); 
        }

Fork:

 int pid = fork();
        if ( pid == 0 ) 
        {
            execl( "udp-proxy/udp_proxy","udp-proxy/udp_proxy",listenPort.c_str(),listenClient.c_str(),listenHost.c_str(),nullptr );
        }

However, afrer I restart the "launcher", it shows a message: "Launher: Can't bind our address".

I checked with "lsof -i UDP", and it seems that child processes are listening to this port, so it can't be binded again. Is it possible to prevent child process using the same binded sockets? I read something about "file descriptors" but I don't know how to prevent it :(

Answer 1

Thanks to @Dietrich Epp for solution.

Adding SOCK_CLOEXEC flag fixes the problem.

Before:

int os=socket(PF_INET,SOCK_DGRAM,IPPROTO_IP);

After:

int os=socket(PF_INET,SOCK_DGRAM|SOCK_CLOEXEC,IPPROTO_IP);