sockets: add a tcp client example

2 files changed, 223 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 686a8d7..9ff95e4 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 BINS = ascii class depipe_strings dup fpipe pipe realloc strpbrk strsep \
        tokenizer getopt prime_mask linked_list pi_bbp string_tokenizer  \
-       tcpserver
+       tcpserver tcpclient
 CC = gcc
 CFLAGS = -Wall -std=gnu99 -pedantic
 DBGFLAGS = -g -O0
diff --git a/tcpclient.c b/tcpclient.c
new file mode 100644
index 0000000..3410b97
--- /dev/null
+++ b/tcpclient.c
@@ -0,0 +1,222 @@
+/* tcpclient.c
+ *
+ * TCP Client
+ * note: 'echo "hello" | nc -l -p 8080 localhost'
+ *
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <sys/socket.h>
+#include <sys/select.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+
+#define TARGET_MAX_SZ 1*1024*1024
+
+static int sockfd;
+static struct addrinfo *res;
+static char *recv_buff;
+
+void cleanup(void)
+{
+    shutdown(sockfd, SHUT_RDWR);
+    close(sockfd);
+
+    if (recv_buff)
+        free(recv_buff);
+
+    /* free the linked list */
+    if (res)
+        freeaddrinfo(res);
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2)
+    {
+        fprintf(stderr, "usage: %s <host>\n", argv[0]);
+        exit(-1);
+    }
+    if (!strstr(argv[1], "http://"))
+    {
+        fprintf(stderr, "host needs to prefixed with \"http://\" protocol\n");
+        exit(-1);
+    }
+
+    /* grab the host and path from the URL */
+    char hoststr[100] = { 0 }, pathstr[100] = { 0 }, filestr[100] = { 0 };
+    sscanf(argv[1], "http://%[^/]/%s", hoststr, pathstr);
+    printf("host is: \"%s\"\n"
+           "path is: \"%s\"\n", hoststr, pathstr);
+
+    /* parse out a filestrname */
+    char *filepart = strrchr(pathstr, '/');
+    if (filepart && strlen(filepart + 1))
+        strcpy(filestr, filepart + 1);
+    else 
+        strcpy(filestr, "index.html");
+    printf("file is: \"%s\"\n", filestr);
+
+    int ret;
+
+    /* prepare for getaddrinfo call */
+    struct addrinfo hints;
+    memset(&hints, 0, sizeof hints);
+    hints.ai_family = AF_UNSPEC;
+    hints.ai_socktype = SOCK_STREAM;
+
+    if ((ret = getaddrinfo(hoststr, "http", &hints, &res)) != 0)
+    {
+        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(ret));
+        exit(-1);
+    }
+
+    /* try all available IP addresses */
+    struct addrinfo *p;
+    char ipstr[INET6_ADDRSTRLEN];
+    void *addr;
+    char *ipver;
+    struct sockaddr_in *ipv4;
+#if 0
+    struct sockaddr_in6 *ipv6;
+#endif
+
+    printf("trying all available IP addresses for %s:\n", hoststr);
+    for (p = res; p != NULL; p = p->ai_next)
+    {
+        /* get the pointer to the address itself,
+         * different fields in IPv4 and IPv6 */
+        if (p->ai_family == AF_INET)
+        {   /* IPv4 */
+            ipv4 = (struct sockaddr_in *) p->ai_addr;
+            addr = &(ipv4->sin_addr);
+            ipver = "IPv4";
+        }
+        else
+            continue; /* ignore IPv6 for now */
+#if 0
+        else
+        {   /* IPv6 */
+            ipv6 = (struct sockaddr_in6 *) p->ai_addr;
+            addr = &(ipv6->sin6_addr);
+            ipver = "IPv6";
+        }
+#endif
+
+        /* convert the IP to a string and print it */
+        inet_ntop(p->ai_family, addr, ipstr, sizeof(ipstr));
+        printf("attempting to connect to %s: %s\n", ipstr, ipver);
+
+        /* create a socket */
+        if ((sockfd = socket(p->ai_family, p->ai_socktype, res->ai_protocol)) == -1)
+        {
+            perror("socket");
+            close(sockfd);
+        }
+
+        /* attempt to connect */
+        if (connect(sockfd, (struct sockaddr *) ipv4, sizeof(*ipv4)) == -1)
+            perror("connect");
+        else
+        {
+            printf("successfully connected\n");
+            break; /* break out of a loop, we got a connection */
+        }
+    }
+
+    if (!p)
+    {
+        fprintf(stderr, "failed to connect to a host\n");
+        exit(-1);
+    }
+
+    atexit(cleanup);
+
+    /* send http commands and receive data */
+    char request[128] = { 0 };
+    sprintf(request, "GET /%s HTTP/1.0\r\nHost: %s\r\n\r\n", pathstr, hoststr);
+    size_t request_len = strlen(request) * sizeof(char);
+
+    ret = send(sockfd, (void *) request, request_len, 0);
+    if (ret == -1)
+    {
+        perror("send");
+        exit(-1);
+    }
+    else if (ret != request_len)
+    {
+        fprintf(stderr, "sent less bytes than requested\n");
+        exit(-1);
+    }
+
+    /* receive until connection gets closed */
+    recv_buff = (char *) malloc(sizeof(char) * TARGET_MAX_SZ);
+    if (!recv_buff)
+    {
+        perror("malloc");
+        exit(-1);
+    }
+    size_t recv_len = 0;
+
+    do
+    {
+        ret = recv(sockfd, recv_buff + recv_len, TARGET_MAX_SZ - recv_len, 0);
+        if (ret == -1)
+        {
+            perror("recv");
+            exit(-1);
+        }
+        else if (ret == 0)
+            printf("remote host has closed the connection, received %lu bytes\n", recv_len);
+
+        recv_len += ret;
+
+    } while (ret > 0);
+
+    if (recv_len < 1)
+    {
+        fprintf(stderr, "did not receive any data from the host!\n");
+        exit(-1);
+    }
+
+    /* poke at http header and check for errors */
+    int code;
+    sscanf(recv_buff, "HTTP/1.%*[01] %d ", &code);
+    if (code == 200) 
+        printf("received file\n");
+    else
+    {
+        printf("got an error code %d\n", code);
+        char errorline[100];
+        sscanf(recv_buff, "%[^\r\n]", errorline);
+        fprintf(stderr, "%s\n", errorline);
+        exit(-1);
+    }
+
+    /* save to disk */
+    char *buff_p = strstr(recv_buff, "\r\n\r\n"); /* seek past http header */
+    if (buff_p)
+    {
+        buff_p += 4;
+
+        FILE *fp = fopen(filestr, "w");
+        if (!fp)
+        {
+            perror("fopen");
+            exit(-1);
+        }
+
+        ret = fwrite(buff_p, recv_len - (buff_p - recv_buff), sizeof(char), fp);
+        fclose(fp);
+    }
+    else
+        fprintf(stderr, "could not seek past http header\n");
+}
+