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#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <assert.h>
#if EMSCRIPTEN
#include <emscripten.h>
#endif
#define EXPECTED_BYTES 5
int SocketFD;
int done = 0;
void iter(void *arg) {
static int state = 0;
static char writebuf[] = "01234567890123456789";
static int writePos = 0;
static char readbuf[1024];
static int readPos = 0;
int selectRes;
ssize_t transferAmount;
fd_set sett;
switch( state ){
case 0:
// writing 10 bytes to the server
// the socket in the read file descriptors has to result in a 0 return value
// because the connection exists, but there is no data yet
FD_ZERO( &sett );
FD_SET(SocketFD, &sett);
selectRes = select(64, &sett, NULL, NULL, NULL);
if( selectRes != 0 ){
printf( "case 0: read select != 0\n" );
exit(EXIT_FAILURE);
}
// the socket in the write file descriptors has to result in either a 0 or 1
// the connection either is setting up or is established and writing is possible
FD_ZERO( &sett );
FD_SET(SocketFD, &sett);
selectRes = select(64, NULL, &sett, NULL, NULL);
if( selectRes == -1 ){
printf( "case 0: write select == -1\n" );
exit(EXIT_FAILURE);
}
if( selectRes == 0 ){
return;
}
// send a single byte
transferAmount = send( SocketFD, writebuf+writePos, 1, 0 );
writePos += transferAmount;
// after 10 bytes switch to next state
if( writePos >= 10 ){
state = 1;
}
break;
case 1:
// wait until we can read one byte to make sure the server
// has sent the data and then closed the connection
FD_ZERO( &sett );
FD_SET(SocketFD, &sett);
selectRes = select(64, &sett, NULL, NULL, NULL);
if( selectRes == -1 ){
printf( "case 1: read selectRes == -1\n" );
exit(EXIT_FAILURE);
}
if( selectRes == 0 )
return;
// read a single byte
transferAmount = recv( SocketFD, readbuf+readPos, 1, 0 );
readPos += transferAmount;
// if successfully reading 1 byte, switch to next state
if( readPos >= 1 ){
state = 2;
}
break;
case 2:
// calling select with the socket in the write file descriptors has
// to fail because the tcp network connection is already down
FD_ZERO( &sett );
FD_SET(SocketFD, &sett);
selectRes = select(64, NULL, &sett, NULL, NULL);
if( selectRes != -1 ){
printf( "case 2: write selectRes != -1\n" );
exit(EXIT_FAILURE);
}
// calling select with the socket in the read file descriptors
// has to succeed because there is still data in the inQueue
FD_ZERO( &sett );
FD_SET(SocketFD, &sett);
selectRes = select(64, &sett, NULL, NULL, NULL);
if( selectRes != 1 ){
printf( "case 2: read selectRes != 1\n" );
exit(EXIT_FAILURE);
}
if( selectRes == 0 )
return;
// read a single byte
transferAmount = recv( SocketFD, readbuf+readPos, 1, 0 );
readPos += transferAmount;
// with 10 bytes read the inQueue is empty => switch state
if( readPos >= 10 ){
state = 3;
}
break;
case 3:
// calling select with the socket in the read file descriptors
// now also has to fail as the inQueue is empty
FD_ZERO( &sett );
FD_SET(SocketFD, &sett);
selectRes = select(64, &sett, NULL, NULL, NULL);
if( selectRes != -1 ){
printf( "case 3: read selectRes != -1\n" );
exit(EXIT_FAILURE);
}
// report back success, the 266 is just an arbitrary value without
// deeper meaning
int result = 266;
REPORT_RESULT();
break;
default:
printf( "Impossible state!\n" );
exit(EXIT_FAILURE);
break;
}
return;
}
// This test checks for an intended asymmetry in the behavior of the select function.
// Scenario: the client sends data to the server. After 10 received bytes the
// server sends 10 bytes on its own and immediately afterwards closes the connection.
// This mimics a typical connect-request-response-disconnect situation.
// After the server closed the connection select calls with the socket in the write file
// descriptors have to fail as the tcp connection is already down and there is no way
// anymore to send data.
// Select calls with the socket in the read file descriptor list still have to succeed
// as there are still 10 bytes to read from the inQueue. So, for the same socket the
// select call behaves differently depending on whether the socket is listed in the
// read or write file descriptors.
int main(void)
{
struct sockaddr_in stSockAddr;
int Res;
SocketFD = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
if (-1 == SocketFD)
{
perror("cannot create socket");
exit(EXIT_FAILURE);
}
memset(&stSockAddr, 0, sizeof(stSockAddr));
stSockAddr.sin_family = AF_INET;
stSockAddr.sin_port = htons(
#if EMSCRIPTEN
8999
#else
8998
#endif
);
Res = inet_pton(AF_INET, "127.0.0.1", &stSockAddr.sin_addr);
if (0 > Res) {
perror("error: first parameter is not a valid address family");
close(SocketFD);
exit(EXIT_FAILURE);
} else if (0 == Res) {
perror("char string (second parameter does not contain valid ipaddress)");
close(SocketFD);
exit(EXIT_FAILURE);
}
// This call should succeed (even if the server port is closed)
if (-1 == connect(SocketFD, (struct sockaddr *)&stSockAddr, sizeof(stSockAddr))) {
perror("connect failed");
close(SocketFD);
exit(EXIT_FAILURE);
}
#if EMSCRIPTEN
emscripten_set_main_loop(iter, 0, 0);
#else
while (!done) iter(NULL);
#endif
return EXIT_SUCCESS;
}
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