我编写了一个简单的程序,该程序从stdin
读取输入,并通过TCP将其发送到侦听端口15557的服务器。
当我在Linux下编译并运行它时,它可以正常工作。但是,当我尝试在Cygwin下编译并运行它时,它失败并显示以下错误消息:
$ ./a.out servername.net 15557 < test.dat
Unable to connect: Cannot assign requested address
我已经排除了任何防火墙/网络问题,因为我能够通过telnet连接到同一台服务器并发送手工输入的相同数据。
知道这里出了什么问题吗?
更新
按照@Hasturkun的提示,我已经在GDB下启动了该程序,以检查
gethostbyname
的结果是什么。在gethostbyname
调用之后,就在这里:(gdb) print *serverent
$2 = {h_name = 0x603217 "bilbo.neurobat.net", h_aliases = 0x603030, h_addrtype = 2, h_length = 4, h_addr_list = 0x6031c0}
(gdb) print serverent->h_addr_list[0]
$3 = 0x60322c ">\002V0"
(gdb) print atoi(">\002V0")
$5 = 0
我不明白如何解释“> \ 002V0”字符串。这应该是一个互联网地址吗?
/ UPDATE
FWIW,整个程序如下所示:
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
#include "neurocli.h"
int main(int argc, char* argv[]) {
char *line = NULL;
char buf[40] = {0};
ssize_t write_len = 0, read_len;
size_t n = 0;
int neuro_socket;
if (argc != 3) {
fprintf(stderr, "Usage: %s host port\n", argv[0]);
return -1;
}
neuro_socket = open_tcp_socket(argv[1], atoi(argv[2]));
/* Main loop: connect, write, read, re-connect and finally close */
while ((write_len=getline(&line, &n, stdin)) != -1) {
printf("# %s", line);
if (write(neuro_socket, line, write_len) < 0) {
perror("Unable to write to server");
exit(EXIT_FAILURE);
}
if (*line=='\n') {
read_len = read(neuro_socket, buf, 40);
buf[read_len] = '\0';
printf("%s", buf);
close(neuro_socket);
neuro_socket = open_tcp_socket(argv[1], atoi(argv[2]));
}
free(line);
line = NULL; /* getline() needs this */
}
free(line);
close(neuro_socket);
return 0;
}
int open_tcp_socket(char *server, int port) {
int result;
static struct sockaddr_in *sockaddr;
/* Create socket */
if ((result = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("Unable to create socket");
exit(EXIT_FAILURE);
}
if (sockaddr==NULL)
sockaddr = make_sockaddr(server, port); /* never mind the memory leak */
/* Connect */
if (connect(result, (struct sockaddr*)sockaddr, sizeof(*sockaddr)) != 0) {
perror("Unable to connect");
exit(EXIT_FAILURE);
}
return result;
}
struct sockaddr_in *make_sockaddr(char *name, int port) {
struct sockaddr_in *sockaddr = malloc(sizeof(struct sockaddr_in));
struct hostent *serverent;
memset(sockaddr, 0, sizeof(*sockaddr));
sockaddr->sin_family = AF_INET;
sockaddr->sin_port = htons(port);
if ((serverent = gethostbyname(name)) == NULL) {
perror("Unable to lookup server IP address");
exit(EXIT_FAILURE);
}
sockaddr->sin_addr.s_addr = atoi(serverent->h_addr_list[0]);
return sockaddr;
}
最佳答案
这条线
sockaddr->sin_addr.s_addr = atoi(serverent->h_addr_list[0]);
是不正确的。
h_addr_list
包含struct in_addr
或struct in6_addr
的地址,长度以h_length
给出,并且可以通过h_addrtype
确定类型。要获取地址,请输入
memcpy
或将其分配给适当的类型
关于c - 网络程序可在Linux中运行,而不是在Cygwin下,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/6292945/