我正在尝试使用C程序接受来自Google Server的OAuth 2 authcode（以HTTP GET请求的形式）。如果我尝试使用recv（）读取，则会抛出错误，传输端点未连接。这只是在我接受accept（）调用后收到非负整数之后。我使用Java和Netcat实用程序尝试了相同的操作，对我来说都很好。
这是代码。
#include<stdio.h>
#include<string.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<stdlib.h>
#include<pthread.h>
#include<sys/select.h>
#include<fcntl.h>
#include<errno.h>
void *send_authcode_request(void *sockaddr_ptr);
int main() {
char *bind_addr = "127.0.0.1";
char *errmsg = (char *) malloc(1024);
short int port = 0;
setvbuf(stdout, NULL, _IONBF, 0);
struct sockaddr_in local_addr;
struct sockaddr_in client_addr;
local_addr.sin_family = AF_INET;
local_addr.sin_port = port;
inet_aton(bind_addr, &(local_addr.sin_addr));
memset(&(local_addr.sin_zero), '\0', 8);
int sock_id = socket(AF_INET, SOCK_STREAM, 0);
/*fcntl(sock_id, F_SETFL, O_NONBLOCK);*/
if (bind(sock_id, (struct sockaddr*) &local_addr, sizeof(struct sockaddr)) == -1) {
sprintf(errmsg, "Cannot bind socket to the port #%d", port);
perror(errmsg);
return -1;
}
if (listen(sock_id, 20) == -1) {
sprintf(errmsg, "Cannot listen to connections on the socket");
perror(errmsg);
return -1;
}
int sin_size = sizeof(struct sockaddr_in);
if(getsockname(sock_id, (struct sockaddr *) &local_addr, &sin_size) == -1) {
sprintf(errmsg, "Unable to get the current address of the socket");
perror(errmsg);
return -1;
}
printf("\n Port no after binding #%d\n", ntohs(local_addr.sin_port));
pthread_t authcode_req_thread;
pthread_create(&authcode_req_thread, NULL, send_authcode_request, (void *) &local_addr);
fd_set read_fs;
FD_ZERO(&read_fs);
FD_SET(sock_id, &read_fs);
long accept_timeout = 60*10;
struct timeval tv;
tv.tv_sec = accept_timeout;
tv.tv_usec = 0;
char auth_code_info[1024];
if (select(sock_id+1, &read_fs, NULL, NULL, &tv) > 0) {
/*if(accept4(sock_id, (struct sockaddr *) &client_addr, &sin_size, SOCK_NONBLOCK) == -1) {*/
if(accept(sock_id, (struct sockaddr *) &client_addr, &sin_size) >= 0) {
/* Accept auth code */
int bytesread;
if ((bytesread = recv(sock_id, auth_code_info, 1023, 0)) == -1) {
perror(errmsg);
return -1;
}
printf("\n%s\n", auth_code_info);
char *reply = "Done! You can now close the window";
send(sock_id, reply, strlen(reply), 0);
} else {
sprintf(errmsg, "No client connected within timeout of %ld seconds", accept_timeout);
perror(errmsg);
return -1;
}
} else {
sprintf(errmsg, "No client connected within timeout of %ld seconds", accept_timeout);
perror(errmsg);
return -1;
}
close(sock_id);
printf("\n");
return 0;
}
void *send_authcode_request(void *ptr) {
char *scope = "https://www.googleapis.com/auth/drive";
char *client_id = "1098482466406-c3h15ld90l03s0pl4rm7qq54fcb49t78.apps.googleusercontent.com";
const char *temp_authcode_uri = "xdg-open \"https://accounts.google.com/o/oauth2/v2/auth?scope=%s&redirect_uri=http://127.0.0.1:%d&response_type=code&client_id=%s\"";
struct sockaddr_in *socket_address = (struct sockaddr_in *) ptr;
int max_authcode_uri_len = strlen(temp_authcode_uri) + strlen(client_id) + strlen(scope);
char *authcode_uri = (char *) malloc(max_authcode_uri_len);
sprintf(authcode_uri, temp_authcode_uri, scope, ntohs(socket_address->sin_port), client_id);
printf("\n%s\n", authcode_uri);
system(authcode_uri);
}
但是，当我使用 netcat 收听同一端口时，它会显示来自浏览器的HTTP请求。所以我使用Wireshark跟踪端口的TCP流量，发现一个流量与使用netcat时的流量不同。
No. Time Source Destination Protocol Length Info
1 0.000000000 127.0.0.1 127.0.0.1 TCP 74 48234 → 49927 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7268636 TSecr=0 WS=128
2 0.000010715 127.0.0.1 127.0.0.1 TCP 74 49927 → 48234 [SYN, ACK] Seq=0 Ack=1 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7268636 TSecr=7268636 WS=128
3 0.000020978 127.0.0.1 127.0.0.1 TCP 66 48234 → 49927 [ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=7268636 TSecr=7268636
4 0.000059901 127.0.0.1 127.0.0.1 TCP 74 48236 → 49927 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7268636 TSecr=0 WS=128
5 0.000064624 127.0.0.1 127.0.0.1 TCP 74 49927 → 48236 [SYN, ACK] Seq=0 Ack=1 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7268636 TSecr=7268636 WS=128
6 0.000070536 127.0.0.1 127.0.0.1 TCP 66 48236 → 49927 [ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=7268636 TSecr=7268636
7 0.000384302 127.0.0.1 127.0.0.1 TCP 66 49927 → 48234 [FIN, ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=7268636 TSecr=7268636
8 0.000412860 127.0.0.1 127.0.0.1 TCP 66 49927 → 48236 [RST, ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=7268636 TSecr=7268636
9 0.000997709 127.0.0.1 127.0.0.1 TCP 66 48234 → 49927 [FIN, ACK] Seq=1 Ack=2 Win=43776 Len=0 TSval=7268637 TSecr=7268636
10 0.000974316 127.0.0.1 127.0.0.1 TCP 66 [TCP Keep-Alive] 48234 → 49927 [ACK] Seq=1 Ack=2 Win=43776 Len=0 TSval=7268637 TSecr=7268636
11 0.001005630 127.0.0.1 127.0.0.1 TCP 66 49927 → 48234 [ACK] Seq=2 Ack=2 Win=43776 Len=0 TSval=7268637 TSecr=7268637
12 0.001047174 127.0.0.1 127.0.0.1 TCP 74 48238 → 49927 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7268637 TSecr=0 WS=128
13 0.001051855 127.0.0.1 127.0.0.1 TCP 54 49927 → 48238 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
14 0.237652758 127.0.0.1 127.0.0.1 TCP 74 48240 → 49927 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7268696 TSecr=0 WS=128
15 0.237664760 127.0.0.1 127.0.0.1 TCP 54 49927 → 48240 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
16 5.243733213 127.0.0.1 127.0.0.1 TCP 74 48242 → 49927 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7269947 TSecr=0 WS=128
17 5.243751969 127.0.0.1 127.0.0.1 TCP 54 49927 → 48242 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
使用netcat，我得到包含身份验证令牌的所需HTTP Get请求。
No. Time Source Destination Protocol Length Info
1 0.000000000 127.0.0.1 127.0.0.1 TCP 74 45064 → 2807 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7233868 TSecr=0 WS=128
2 0.000008155 127.0.0.1 127.0.0.1 TCP 74 2807 → 45064 [SYN, ACK] Seq=0 Ack=1 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7233868 TSecr=7233868 WS=128
3 0.000015895 127.0.0.1 127.0.0.1 TCP 66 45064 → 2807 [ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=7233868 TSecr=7233868
4 0.000043941 127.0.0.1 127.0.0.1 TCP 74 45066 → 2807 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7233868 TSecr=0 WS=128
5 0.000047566 127.0.0.1 127.0.0.1 TCP 74 2807 → 45066 [SYN, ACK] Seq=0 Ack=1 Win=43690 Len=0 MSS=65495 SACK_PERM=1 TSval=7233868 TSecr=7233868 WS=128
6 0.000050911 127.0.0.1 127.0.0.1 TCP 66 45066 → 2807 [ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=7233868 TSecr=7233868
7 0.000074583 127.0.0.1 127.0.0.1 TCP 66 2807 → 45066 [RST, ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=7233868 TSecr=7233868
8 0.000833585 127.0.0.1 127.0.0.1 HTTP 654 GET /?code=4/zuPKCQlOvIcJq5gAvPRGLQdkiICNzOmAQUAx9apK5go HTTP/1.1
9 0.000841060 127.0.0.1 127.0.0.1 TCP 66 2807 → 45064 [ACK] Seq=1 Ack=589 Win=44928 Len=0 TSval=7233868 TSecr=7233868
10 45.005118503 127.0.0.1 127.0.0.1 TCP 66 [TCP Keep-Alive] 45064 → 2807 [ACK] Seq=588 Ack=1 Win=43776 Len=0 TSval=7245120 TSecr=7233868
11 45.005166221 127.0.0.1 127.0.0.1 TCP 66 [TCP Keep-Alive ACK] 2807 → 45064 [ACK] Seq=1 Ack=589 Win=44928 Len=0 TSval=7245120 TSecr=7233868
如您所见，我的程序发送FIN标志，netcat中没有。我在哪里错了？
答案 0 :(得分：0)
您正在从错误的套接字读取。
传递给listen的套接字只是一个侦听套接字。它不代表连接的套接字。它仅由本地IP和端口标识。
当您调用accept时，此函数返回已连接套接字的文件描述符。这些套接字由本地IP和端口以及远程IP和端口标识。因此，对于多个传入连接，可以多次调用此函数，每个传入连接都有自己的套接字。这样，您就可以处理来自多个端点的连接。
将accept的返回值保存为新套接字，并将其用于send和recv。
close。