这可能是一个简单的问题,但是当我尝试读取数据时,我尝试使用套接字API修改来自Geeks for Geeks [site] 1的代码来读取服务器响应,它在valread = read(server_fd, buffer, 2048);
行中被永久阻止,并且不执行任何打印。我在做错什么吗?
#include <unistd.h>
#include <stdio.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <errno.h>
int send_request() {
int server_fd, new_socket, valread;
struct sockaddr_in address;
int opt = 1;
int addrlen = sizeof(address);
char buffer[512] = {0};
char *hello = "Hello from server";
// Creating socket file descriptor
if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
perror("socket failed");
exit(EXIT_FAILURE);
}
// Forcefully attaching socket to the port 8080
if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
perror("setsockopt");
exit(EXIT_FAILURE);
}
// CONNECT TO HOST
struct hostent *he;
char* host = "www.columbia.edu";
he = gethostbyname(host);
if(!he) {
printf("Host doesn't exist!\n");
return 0;
}
address.sin_family = AF_INET;
bcopy(he->h_addr, &address.sin_addr, sizeof(struct in_addr));
address.sin_port = htons(80);
if(connect(server_fd, (struct sockaddr *) &address, sizeof(struct sockaddr_in)) < 0) {
printf("Error in the connection");
return 0;
}
valread = read(server_fd, buffer, 2048);
printf("%s\n", buffer);
printf("%d\n", valread);
printf("%d\n", errno);
return 0;
}
int main(int argc, char const *argv[]) {
send_request();
return 0;
}
答案 0 :(得分:2)
您正在连接到HTTP服务器。 HTTP协议指定客户端(即与服务器建立连接的一方)必须首先发送请求。您没有发送请求,因此服务器不会向您发送回复。
另外,这是一个错误:
valread = read(server_fd, buffer, 2048);
printf("%s\n", buffer);
%s
格式说明符只能与C样式的字符串一起使用。不能用于任意数据。一方面,它如何知道要输出多少字节?当前包含信息的唯一位置是valread
,您没有将其传递给printf
。