From: Ajay DOT Desai AT mci DOT com ("Ajay M. Desai") Subject: Bug in socket fork code? 30 Dec 1996 15:41:10 -0800 Sender: daemon AT cygnus DOT com Approved: cygnus DOT gnu-win32 AT cygnus DOT com Distribution: cygnus Message-ID: <32C84F59.6686.cygnus.gnu-win32@mci.com> Reply-To: Ajay DOT Desai AT mci DOT com Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------23CB2AD741CF" X-Mailer: Mozilla 3.0Gold (WinNT; I) Original-To: gnu-win32 AT cygnus DOT com Original-Sender: owner-gnu-win32 AT cygnus DOT com This is a multi-part message in MIME format. --------------23CB2AD741CF Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit The following code compiles but hangs. If the server fork is removed it works just fine. -- |-----------------------------------------------------| | Ajay M. Desai | | Software Engineering Consultant MCI Metro | | Home: mailto:adesai AT erol DOT com Vienna, VA | | Work: mailto:Ajay DOT Desai AT mci DOT com 703 918-0845 | | MCI Mail ID: 214-0881 | |-----------------------------------------------------| --------------23CB2AD741CF Content-Type: text/plain; charset=us-ascii; name="server.c" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="server.c" /* * Connects to port 1234 on the local host. */ #include #include #include #include #include #include #include #define NSTRS 3 /* no. of strings */ /* * Strings we send to the client. */ char *strs[NSTRS] = { "This is the first string from the server.\n", "This is the second string from the server.\n", "This is the third string from the server.\n" }; extern int errno; int main() { char c; FILE *fp; int fromlen; char hostname[64]; struct hostent *hp; register int i, s, ns; struct sockaddr_in sin, fsin; /* * Before we can do anything, we need * to know our hostname. */ gethostname(hostname, sizeof(hostname)); /* * Now we look up our host to get * its network number. */ if ((hp = gethostbyname(hostname)) == NULL) { fprintf(stderr, "%s: host unknown.\n", hostname); exit(1); } /* * Get a socket to work with. This socket will * be in the Internet domain, and will be a * stream socket. */ if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) { perror("server: socket"); exit(1); } /* * Create the address that we will be binding to. * We use port 1234 but put it into network * byte order. Also, we use bcopy (see * Chapter 14) to copy the network number. */ sin.sin_family = AF_INET; sin.sin_port = htons(1234); bcopy(hp->h_addr, &sin.sin_addr, hp->h_length); /* * Try to bind the address to the socket. */ if (bind(s, (struct sock_addr*)&sin, sizeof(sin)) < 0) { perror("server: bind"); exit(1); } /* * Listen on the socket. */ if (listen(s, 5) < 0) { perror("server: listen"); exit(1); } while(1){ /* * Accept connections. When we accept one, ns * will be connected to the client. fsin will * contain the address of the client. */ if ((ns = accept(s, (struct sock_addr*)&fsin, &fromlen)) < 0) { perror("server: accept"); exit(1); } if (fork() == 0){ /* * We'll use stdio for reading the socket. */ fp = fdopen(ns, "r"); /* * First we send some strings to the client. */ for (i = 0; i < NSTRS; i++) send(ns, strs[i], strlen(strs[i]), 0); /* * Then we read some strings from the client * and print them out. */ for (i = 0; i < NSTRS; i++) { while ((c = fgetc(fp)) != EOF) { putchar(c); if (c == '\n') break; } } /* * We can simply use close() to terminate the * connection, since we're done with both sides. */ close(ns); exit(0); } else{ close(ns); // parent } } return(0); } --------------23CB2AD741CF Content-Type: text/plain; charset=us-ascii; name="client.c" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="client.c" /* * Connects to the local host at port 1234. */ #include #include #include #include #include #include #define NSTRS 3 /* no. of strings */ /* * Strings we send to the server. */ char *strs[NSTRS] = { "This is the first string from the client.\n", "This is the second string from the client.\n", "This is the third string from the client.\n" }; extern int errno; main() { char c; FILE *fp; char hostname[64]; register int i, s; struct hostent *hp; struct sockaddr_in sin; /* * Before we can do anything, we need to know * our hostname. */ gethostname(hostname, sizeof(hostname)); /* * Next, we need to look up the network * address of our host. */ if ((hp = gethostbyname(hostname)) == NULL) { fprintf(stderr, "%s: unknown host.\n", hostname); exit(1); } /* * Get a socket to work with. This socket will * be in the Internet domain, and will be a * stream socket. */ if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) { perror("client: socket"); exit(1); } /* * Create the address we will be connecting to. * We use port 1234 but put it into network * byte order. Also, we use bcopy (see Chapter * 14) to copy the network number. */ sin.sin_family = AF_INET; sin.sin_port = htons(1234); bcopy(hp->h_addr, &sin.sin_addr, hp->h_length); /* * Try to connect to the address. For this to * succeed, the server must already have bound * this address, and must have issued a listen() * request. */ if (connect(s, (struct sock_addr*)&sin, sizeof(sin)) < 0) { perror("client: connect"); exit(1); } /* * We'll use stdio for reading * the socket. */ fp = fdopen(s, "r"); /* * First we read some strings from the server * and print them out. */ for (i = 0; i < NSTRS; i++) { while ((c = fgetc(fp)) != EOF) { putchar(c); if (c == '\n') break; } } /* * Now we send some strings to the server. */ for (i = 0; i < NSTRS; i++) send(s, strs[i], strlen(strs[i]), 0); /* * We can simply use close() to terminate the * connection, since we're done with both sides. */ close(s); exit(0); } --------------23CB2AD741CF Content-Type: text/plain; charset=us-ascii; name="Makefile" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="Makefile" all: server.exe client.exe server.exe: server.c gcc -g -o $@ $< client.exe: client.c gcc -g -o $@ $< --------------23CB2AD741CF-- - For help on using this list, send a message to "gnu-win32-request AT cygnus DOT com" with one line of text: "help".