This thread has some useful discussions on this topic. It turns out that Socket.isConnected returns true if it has (ever) been successfully connected. From the above thread: When you use Socket(), which you seem to have overlooked, Socket.isConnected() tells you whether Socket.connect() has been called or not. Similarly for isClosed() and close(). Confusion over these … Read more
A client socket does not listen for incoming connections, it initiates an outgoing connection to the server. The server socket listens for incoming connections. A server creates a socket, binds the socket to an IP address and port number (for TCP and UDP), and then listens for incoming connections. When a client connects to the … Read more
You can’t open a port below 1024, if you don’t have root privileges and from the code you posted in your comment, you seem to be trying to open port 100 which confirms my theory. You need to use a port which is higher than 1024, if you’re running the code under a non-root user.
One solution that I found (although it might not be the most “elegant” solution is using conn.poll. (documentation) Poll returns True if the Listener has new data, and (most importantly) is nonblocking if no argument is passed to it. I’m not 100% sure that this is the best way to do this, but I’ve had … Read more
The best way to go is to use getaddrinfo(). Pseudo code: struct addrinfo *restrict hints = { .ai_family = AF_UNSPEC, .ai_socktype = SOCK_STREAM }; struct addrinfo * res, r; if (0 == getaddrinfo(“foo.bar.baz”, “http”, &hints, &res)) { for (r=res; r; r=r->ai_next) { sock = socket(r->ai_family, r->ai_socktype, r->ai_protocol); connect(sock, r->ai_addr, r->ai_addrlen); if error: continue break } … Read more
Several of the socket options are handled at lower levels of the system. While most of the socket options could be set using the setsockopt. Reference:man setsockopt And since you are mentioning only POSIX on any Linux, in general, as your scope. The accept() (Reference: man accept) does have a certain amount of discretion on … Read more
The format and size of the address is usually protocol specific. sockaddr is used as the base of a set of address structures that act like a discriminated union, see the Beej guide to networking. You generally look at the sa_family and then cast to the appropriate address family’s specific address structure. TCP and UDP … Read more
A TCP connection is uniquely identified by two (IP address, TCP port) tuples (one for each endpoint). So by definition, one can’t move a port or IP address of a connection but just open a different one. If the server binds to port 28081 all accepted connections will have this port on the server side … Read more
But the exception you are getting is exactly this! It’s telling you that the other side just died. Just catch the exception and print to the console, that “The system has detected that KnockKnockServer was aborted”. You are using TCP connection and TCP has built-in heartbeat (keepalive) mechanism that will do this for you. Just … Read more
Another solution is to create a directory with the desired permissions, and then create the socket inside it (example code without any regard for error checking and buffer overflows): // Create a directory with the proper permissions mkdir(path, 0700); // Append the name of the socket strcat(path, “/socket_name”); // Create the socket normally sockaddr_un address; … Read more