c - GET 请求只获取空字符串

Question

我得到了一个示例 C 代码，它将用户输入的请求发送到指定的服务器并打印响应。现在我应该更改代码，以便将 HTTP 请求发送到 http://www.stardrifter.org/cgi-bin/ref.cgi带有 Referer header 集。请求已成功发送，但我只得到空字符串作为响应。

我已经尝试发送最少的 GET 请求，并将来自 Postman 的工作请求粘贴到代码中，但我总是只得到一个空字符串作为响应。此外，我实际上需要很长时间才能收到回复，通常在 1 到 2 分钟之间。

到目前为止，这是我的代码。建立连接似乎工作正常，但形成和发送请求并没有按照我的预期进行:

#include <stdbool.h>     // use booleans in C
#include <stdlib.h>      // use common functions
#include <stdio.h>       // use input/output functions
#include <string.h>      // use string functions
#include <unistd.h>      // use POSIX functions

#include <sys/socket.h>  // use socket function
#include <netinet/in.h>  // use internet address datatypes
#include <arpa/inet.h>   // use inet_ntoa function
#include <netdb.h>       // use network database functions

int main(int argc, char *argv[]) {
    char *hostname = "stardrifter.org";
    int port = 80;

    /** -- Setup connection -- */

    // Get server host information
    struct hostent *serverInfo = gethostbyname(hostname);
    if (serverInfo == NULL) {
        printf("Failed to get info for host '%s'!\n", hostname);
        return -1;
    }

    // Create TCP/IP socket
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock < 0) {
        printf("Failed to create socket!\n");
        return -1;
    }

    // Set address and port of server
    struct sockaddr_in serverAddr;
    serverAddr.sin_family = serverInfo->h_addrtype;
    serverAddr.sin_port = htons(port);
    memcpy(&serverAddr.sin_addr.s_addr, serverInfo->h_addr, serverInfo->h_length);

    // Connect to server
    if (connect(sock, (struct sockaddr *) &serverAddr, sizeof(serverAddr)) < 0) {
        printf("Failed to connect to server at %s:%d!\n",
               inet_ntoa(serverAddr.sin_addr), ntohs(serverAddr.sin_port));
        return -1;
    } else {
        printf("Connected to server at %s:%d\n\n",
               inet_ntoa(serverAddr.sin_addr), ntohs(serverAddr.sin_port));
    }

    /** -- Main program -- */

    char buffer[1024];
    int len = 0;

    char *request = "GET /cgi-bin/ref.cgi HTTP/1.1\r\nHost: www.stardrifter.org\r\nReferer: I'm a Referer\r\n\r\n";

    memset(buffer, 0, 1024);
    strncpy(buffer, request, sizeof buffer - 1);

    // Send message to server
    if (send(sock, buffer, len, 0) < 0) {
        printf("Failed to send message to server!\n");
    } else {
        printf("Sent message to server: \"%s\"\n", buffer);
    }

    // Receive response from server
    printf("Waiting for response...\n");
    memset(buffer, 0, 1024);
    if (recv(sock, buffer, 1024, 0) < 0) {
        printf("Failed to receive response from server!\n");
    }

    // Print received response
    printf("Received response from server: \"%s\"\n", buffer);

    // Close socket
    close(sock);

    return 0;
}

我期望一个带有 html 正文的有效 HTTP 响应，但我的程序只给出:

Connected to server at 69.164.214.143:80

Sent message to server: "GET /cgi-bin/ref.cgi HTTP/1.1
Host: www.stardrifter.org
Referer: I'm a Referer

"
Waiting for response...
Received response from server: ""

Process finished with exit code 0

我不确定，如果我真的得到这个“”作为回应，或者是否有什么。就像超时，然后他只是读取空缓冲区。

Answer 1

您正在发送零字节:

char buffer[1024];
int len = 0;

char *request = "GET /cgi-bin/ref.cgi HTTP/1.1\r\nHost: www.stardrifter.org\r\nReferer: I'm a Referer\r\n\r\n";

memset(buffer, 0, 1024);
strncpy(buffer, request, sizeof buffer - 1);

// Send message to server
if (send(sock, buffer, len, 0) < 0) {
    printf("Failed to send message to server!\n");
} else {
    printf("Sent message to server: \"%s\"\n", buffer);
}

或

int len = 0;

...

if (send(sock, buffer, len, 0) < 0) {
...

为什么要将 request 复制到 buffer？这有效:

ssize_t bytes_sent = send( sock, request, strlen( request ), 0 );

send() 和recv() 都返回发送或接收的字节数。他们这样做是有充分理由的。您需要检查该返回值并确保它完全您所期望的。

此外，send() 的第三个参数是 size_t，而不是 int。