Keep a copy of the IBM manuals handy: z/OS V1R11.0 XL C/C++ Programming Guide z/OS V1R11.0 XL C/C++ Run-Time Library Reference The IBM publications are generally very good, but you need to get used to their format, as well as knowing where to look for an answer. You’ll find quite often that a feature that … Read more
This is caused by: most usually, writing to a connection when the other end has already closed it; less usually, the peer closing the connection without reading all the data that is already pending at his end. So in both cases you have a poorly defined or implemented application protocol. There is a third reason … Read more
TCP / HTTP Listening On Ports: How Can Many Users Share the Same Port So, what happens when a server listen for incoming connections on a TCP port? For example, let’s say you have a web-server on port 80. Let’s assume that your computer has the public IP address of 24.14.181.229 and the person that … Read more
Do not bind to a specific port. Instead, bind to port 0: import socket sock = socket.socket() sock.bind((”, 0)) sock.getsockname()[1] The OS will then pick an available port for you. You can get the port that was chosen using sock.getsockname()[1], and pass it on to the slaves so that they can connect back. sock is … Read more
When you send bytes from a buffer with a normal TCP socket, the send function returns the number of bytes of the buffer that were sent. If it is a non-blocking socket or a non-blocking send then the number of bytes sent may be less than the size of the buffer. If it is a … Read more
Well, the most likely difference is that you still have to do an actual lookup of localhost somewhere. If you use 127.0.0.1, then (intelligent) software will just turn that directly into an IP address and use it. Some implementations of gethostbyname will detect the dotted format (and presumably the equivalent IPv6 format) and not do … Read more
If you don’t mind the port used, specify a port of 0 to the ServerSocket constructor and it will listen on any free port. ServerSocket s = new ServerSocket(0); System.out.println(“listening on port: ” + s.getLocalPort()); If you want to use a specific set of ports, then the easiest way is probably to iterate through them … Read more
What is the difference between connection and read timeout for sockets? The connection timeout is the timeout in making the initial connection; i.e. completing the TCP connection handshake. The read timeout is the timeout on waiting to read data1. If the server (or network) fails to deliver any data <timeout> seconds after the client makes … Read more
This generally means that the remote side closed the connection (usually by sending a TCP/IP RST packet). If you’re working with a third-party application, the likely causes are: You are sending malformed data to the application (which could include sending an HTTPS request to an HTTP server) The network link between the client and server … Read more
It is true that a typical IPv4 header is 20 bytes, and the UDP header is 8 bytes. However it is possible to include IP options which can increase the size of the IP header to as much as 60 bytes. In addition, sometimes it is necessary for intermediate nodes to encapsulate datagrams inside of … Read more