#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <unistd.h>


int
main(int argc, const char* const* argv)
{
        // create the listener socket
        int listenerSocket = socket(AF_INET, SOCK_STREAM, 0);
        if (listenerSocket < 0) {
                fprintf(stderr, "failed to create listener socket: %s\n",
                        strerror(errno));
                exit(1);
        }

        // bind it to the port
        sockaddr_in addr;
        addr.sin_family = AF_INET;
        addr.sin_addr.s_addr = INADDR_ANY;
        addr.sin_port = 0;
        socklen_t addrLen = sizeof(addr);
        if (bind(listenerSocket, (sockaddr*)&addr, addrLen) < 0) {
                fprintf(stderr, "failed to bind listener socket: %s\n",
                        strerror(errno));
                exit(1);
        }

        memset(&addr, 0, sizeof(addr));
        addrLen = sizeof(addr);
        if (getsockname(listenerSocket, (sockaddr*)&addr, &addrLen) != 0) {
                fprintf(stderr, "failed to get socket name: %s\n", strerror(errno));
                exit(1);
        }

        printf("listener port: %d (%x)\n", addr.sin_port, addr.sin_addr.s_addr);

        // start listening
        if (listen(listenerSocket, 1) < 0) {
                return -1;
        }

        // fork client
        pid_t child = fork();
        if (child < 0) {
                fprintf(stderr, "fork() failed: %s\n", strerror(errno));
                exit(1);
        }

        if (child == 0) {
                // child
                unsigned short previousPort = 0;

                for (int i = 0; ; i++) {
                        // create the client socket
                        int fd = socket(AF_INET, SOCK_STREAM, 0);
                        if (fd < 0) {
                                fprintf(stderr, "child: %d: failed to create client socket: "
                                        "%s\n", i, strerror(errno));
                                exit(1);
                        }

/*
                        // test binding
                        if (previousPort != 0) {
                                sockaddr_in clientAddr;
                                clientAddr.sin_family = AF_INET;
                                clientAddr.sin_addr.s_addr = INADDR_ANY;
//                              clientAddr.sin_addr.s_addr = INADDR_LOOPBACK;
//                              clientAddr.sin_port = htons(previousPort);
//                              clientAddr.sin_port = htons(previousPort + 1);
                                clientAddr.sin_port = htons(25432);
                                if (bind(fd, (sockaddr*)&clientAddr, sizeof(clientAddr)) < 0) {
                                        fprintf(stderr, "child: %d: failed to bind: %s\n",
                                                i, strerror(errno));
                                }
                        }
*/

                        // connect to server
                        if (connect(fd, (sockaddr*)&addr, addrLen) == 0) {
                                sockaddr_in serverAddr;
                                socklen_t serverAddrLen = sizeof(serverAddr);
                                sockaddr_in clientAddr;
                                socklen_t clientAddrLen = sizeof(clientAddr);
                                if (getsockname(fd, (sockaddr*)&clientAddr, &clientAddrLen)
                                                == 0
                                        && getpeername(fd, (sockaddr*)&serverAddr, &serverAddrLen)
                                                == 0) {
                                        previousPort = ntohs(clientAddr.sin_port);
                                        printf("child: %d: connected to server: 0x%08x:%u, "
                                                "local port: %u\n", i,
                                                (unsigned)ntohl(serverAddr.sin_addr.s_addr),
                                                ntohs(serverAddr.sin_port),
                                                previousPort);
                                } else {
                                        fprintf(stderr, "child: %d: failed to get socket name %s\n",
                                                i, strerror(errno));
                                }
                        } else {
                                fprintf(stderr, "child: %d: connect() failed %s\n", i,
                                        strerror(errno));
                        }

                        // wait for the other end to be closed
                        char buffer[1];
                        if (fd >= 0) {
                                read(fd, buffer, sizeof(buffer));
                                close(fd);
                        }

//                      close(fd);
//                      sleep(1);
                }
        } else {
                // parent
                while (true) {
                        // accept a socket
                        int fd = accept(listenerSocket, NULL, 0);
                        if (fd < 0) {
                                fprintf(stderr, "server: accept() failed: %s\n",
                                        strerror(errno));
                                exit(1);
                        }

                        // wait for it to be closed
//                      char buffer[1];
//                      read(fd, buffer, sizeof(buffer));
//                      close(fd);

                        sleep(1);
                        close(fd);
                }
        }

        printf("Everything went fine.\n");
        
        return 0;
}