Interrupted System Call Error
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Interrupted System Calls In Unix
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Interrupted System Call Select
vote favorite I am trying to implement a TCP server and client in C, running on Solaris. I am new to sockets and am using Beej's Guide as an example. For starters, what I would like is for the client to send a message to the server in the form of word1 word2. Upon receipt, I want the server to extract word2 from the message and send that back to the interrupted system call c client. The initial client --> server message sending works fine. But the server --> client response is not working. There are several failure symptoms: The server does not appear to even try to send() anything to the client. After receiving the client's message, the server prints: accept: Interrupted system call, then returns to the top of the while(1) loop and remains there until I Ctrl-C out of it. The client's call to recv() returns 0 bytes. I found an old thread here, where the last post says this: accept is being interrupted by the child process sending a signal back to the parent when it terminates (SIGCHLD, if I remember write). You can either ignore SIGCHLD, or you can code accept() to handle the interrupt better (errno is set to EINTR) However, I'm not understanding this. Why is the child process terminating before even attempting the send() portion? What does "handle the interrupt better" mean? After searching some more, I found this question on Stack Overflow: How to handle EINTR (interrupted System Call). I tried adding the code in the accepted answer, replacing write() with send(), but I still see the same behavior. Server code: #include errno was set to EINTR. This was done under the assumption that since a signal occurred and the process caught it, there is a good chance that something has happened that should wake up the blocked system call. Here, we have to differentiate between a system call and a function. It is a system call within the kernel that is interrupted when a signal is caught. To support this feature, the system calls are divided top: failed tty set: into two categories: the "slow" system calls and all the others. The slow system calls are those that can block forever. Included in this category are Reads that can block the caller forever if data isn't present with http://stackoverflow.com/questions/20067657/tcp-sockets-server-fails-to-respond-to-client-accept-interrupted-system-call certain file types (pipes, terminal devices, and network devices)Writes that can block the caller forever if the data can't be accepted immediately by these same file typesOpens that block until some condition occurs on certain file types (such as an open of a terminal device that waits until an attached modem answers the phone)The pause function (which by definition puts the calling process to sleep until a signal is caught) and the wait functionCertain ioctl operationsSome of http://poincare.matf.bg.ac.rs/~ivana/courses/tos/sistemi_knjige/pomocno/apue/APUE/0201433079/ch10lev1sec5.html the interprocess communication functions (Chapter 15) The notable exception to these slow system calls is anything related to disk I/O. Although a read or a write of a disk file can block the caller temporarily (while the disk driver queues the request and then the request is executed), unless a hardware error occurs, the I/O operation always returns and unblocks the caller quickly. One condition that is handled by interrupted system calls, for example, is when a process initiates a read from a terminal device and the user at the terminal walks away from the terminal for an extended period. In this example, the process could be blocked for hours or days and would remain so unless the system was taken down. POSIX.1 semantics for interrupted reads and writes changed with the 2001 version of the standard. Earlier versions gave implementations a choice for how to deal with reads and writes that have processed partial amounts of data. If read has received and transferred data to an application's buffer, but has not yet received all that the application requested and is then interrupted, the operating system could either fail the system call with errno set to EINTR or allow the system call to succeed, returning the partial amount of data received. Similarly, if write is interrupted after transferring some of the data in an application's buffer, the från GoogleLogga inDolda fältSök efter grupper eller meddelanden socket - UNIX Programming Hello, I have a server application and a client one which communicate with sockets and SSH tunneling (ssh -N -f -L8888:localhost:3333 userlocalhost). I have to use ssh tunneling because of firewalls. My problem is that the read in the client has the "Interrupted system call" error even if I put this while(-1==(nr=read(DIST,ptr,nl))) { if(errno!=EINTR) break; } and it appears randomly. If I do not use ssh tunneling, it works. If someone has an idea ... Thanks, Karim.... Thread Tools Show Printable Version Email this Page… Subscribe to this Thread… Display Linear Mode Switch to Hybrid Mode Switch to Threaded Mode January 9th,07:19 PM #1 "Interrupted system call", read and socket Hello, I have a server application and a client one which communicate with sockets and SSH tunneling (ssh -N -f -L8888:localhost:3333 userlocalhost). I have to use ssh tunneling because of firewalls. My problem is that the read in the client has the "Interrupted system call" error even if I put this while(-1==(nr=read(DIST,ptr,nl))) { if(errno!=EINTR) break; } and it appears randomly. If I do not use ssh tunneling, it works. If someone has an idea ... Thanks, Karim. karim Guest January 10th,09:29 AM #2 Re: "Interrupted system call", read and socket karim bernardet wrote: No idea. Typically, you will receive this error when the syscall blocks and a signal is delivered. However why bother, just resume read(). E.g.: int readn(int fd, void* data, size_t size) { for (;;) { ssize_t n = read(fd, data, size); if (n == -1) { if (errno == EINTR) continue; // Resume. return errno; } if (!(size -= n)) return 0; data = (char*)data + n; } } /FAU Frank Guest January 11th,03:22 PM #3 Re: "Interrupted system call", read and socket Hello Karim, [/ref] So basically, you resume the read() and you still get an "Interrupted system call"? Whether your loop construct is wrong (doesn't look like to me. Though I prefer Frank's construct which is somewhat nicier to read)... Or it's not the read() call that got interrupted... Regards, Loic. Loic Guest « Help: how to change indent character in VI? | Finding Skeleton Daemon Code » Similar Threads How to call the operation-system "Save As" DialogueBox By fighttodeath in forum Macromedia Flex General Discussion Replies: 7 Last Post: June 2nd, 07:35 PM CALL TO ACTION: Photoshop GURU's help solve "BULGEGATE"... please read By political commentator in forum Adobe Flash, Flex & Director RepliesInterrupted System Call Recv
Interrupted System Call (code=4)