我正在尝试用C语言实现一个简单的客户端和服务器，但我在网上找不到如何为客户端设置特定IP地址的示例。目前我已经做到了这一步：
sockfd = socket(PF_INET, SOCK_STREAM, 0);
if (sockfd == -1)
{
<some code to handle error>
}
address.sin_family = AF_INET;
address.sin_addr.s_addr = inet_addr(<addressOfTheServer>);
address.sin_port = htons(<portToConnectToServer>);
len = sizeof(address);
int result = connect(sockfd, (struct sockaddr *)&address, len);
在服务器端，我检查客户端IP地址，但我总是得到127.0.0.1。
我想把它改成不同的东西。
如果您希望客户端使用特定的网络接口连接（例如，因为您有多个网络卡），则需要先在该接口的IP地址上调用bind(2)，然后再进行connect操作。例如，如果您有两个网络接口，其IP地址分别是192.168.1.100和10.101.151.100，则可以按照以下方式使用192.168.1.100地址进行连接：
// Error checking omitted for expository purposes
int sockfd = socket(AF_INET, SOCK_STREAM, 0);
// Bind to a specific network interface (and optionally a specific local port)
struct sockaddr_in localaddr;
localaddr.sin_family = AF_INET;
localaddr.sin_addr.s_addr = inet_addr("192.168.1.100");
localaddr.sin_port = 0; // Any local port will do
bind(sockfd, (struct sockaddr *)&localaddr, sizeof(localaddr));
// Connect to the remote server
struct sockaddr_in remoteaddr;
remoteaddr.sin_family = AF_INET;
remoteaddr.sin_addr.s_addr = inet_addr(server_ip);
remoteaddr.sin_port = htons(server_port);
connect(sockfd, (struct sockaddr *)&remoteaddr, sizeof(remoteaddr));
好的，所以我将解决方案与从计算机获取IP地址组合在一起：
/*dl_senderprog.c - debian linux send to server a client, datagram*/
/***********************************************************************
140203 lets see if we can bind to a port
ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
ts7500:/var/www/jon/uvir_sensor_lab/source/socket# vi senderprog_bind.c
ts7500:/var/www/jon/uvir_sensor_lab/source/socket# gcc -g senderprog_bind.c -o senderprog_bind
ts7500:/var/www/jon/uvir_sensor_lab/source/socket# ./senderprog_bind
Sender:Client-Usage: ./senderprog_bind <hostname> <message>
ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
ts7500:/var/www/jon/uvir_sensor_lab/source/socket# ./senderprog_bind 10.0.1.26 "dot,33,22"
MY IP address:10.0.1.242: on port: 1043
Sender: Client-gethostname() is OK...
Sender: Client-socket() sockfd is OK...
Sender: Using port: 14950
Sender: Client-sendto() is OK...
Sender: sent 9 bytes to 10.0.1.26
Sender: Client-sockfd successfully closed!
ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
ts7500:/var/www/jon/uvir_sensor_lab/source/socket# # it worked!!!!!
ts7500:/var/www/jon/uvir_sensor_lab/source/socket#
***********************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <sys/ioctl.h>
#include <net/if.h>
/* the port users will be connecting to 14950 is the port on the windows machine
that I have the server running on */
#define TOPORT 14950
#define MYPORT 1043
void my_ip( char *myniccard, char *myipaddr) {
int fd;
struct ifreq ifr;
myipaddr[0]=0;
fd = socket(AF_INET, SOCK_DGRAM, 0);
/* I want to get an IPv4 IP address */
ifr.ifr_addr.sa_family = AF_INET;
/* I want IP address attached to "eth0" */
//strncpy(ifr.ifr_name, "eth0", IFNAMSIZ-1);
strncpy(ifr.ifr_name, myniccard, IFNAMSIZ-1);
ioctl(fd, SIOCGIFADDR, &ifr);
close(fd);
/* display result */
sprintf(myipaddr,"%s"
, inet_ntoa(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr));
printf("MY IP address:%s: on port: %d\n", myipaddr, MYPORT);
} // my_ip
int main(int argc, char *argv[ ])
{
int sockfd;
/* connectors address information */
struct sockaddr_in their_addr;
struct sockaddr_in localaddr;
char myipaddressm[22]; //buffer for ip address
char *myniccardm ="eth0"; // check with ipconfig for correct ethernet port
struct hostent *he;
int numbytes;
if (argc != 3) {
fprintf(stderr, "Sender:Client-Usage: %s <hostname> <message>\n", argv[0]);
exit(1);
}
my_ip(myniccardm, myipaddressm);
/* get the host info */
if ((he = gethostbyname(argv[1])) == NULL) {
perror("Sender: Client-gethostbyname() error lol!");
exit(1);
}
else
printf("Sender: Client-gethostname() is OK...\n");
if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("Sender: Client-socket() error lol!");
exit(1);
}
else
printf("Sender: Client-socket() sockfd is OK...\n");
// Bind to a specific network interface
// (this is unusual, as you normally do not want a specific
// port for the client, but we have a specific server in
// this case that will not accept connects unless its on
// a specific port )
localaddr.sin_family = AF_INET;
localaddr.sin_addr.s_addr = inet_addr(myipaddressm);
localaddr.sin_port = htons(MYPORT); // Any local port will do
bind(sockfd, (struct sockaddr *)&localaddr, sizeof(localaddr));
/* host byte order */
their_addr.sin_family = AF_INET;
/* short, network byte order */
printf("Sender: Using port: %d\n",TOPORT);
their_addr.sin_port = htons(TOPORT);
their_addr.sin_addr = *((struct in_addr *)he->h_addr);
/* zero the rest of the struct */
memset(&(their_addr.sin_zero), '\0', 8);
if((numbytes = sendto(sockfd, argv[2],
strlen(argv[2]),
0,
(struct sockaddr *)&their_addr,
sizeof(struct sockaddr))) == -1) {
perror("Sender: Client-sendto() error lol!");
exit(1);
}
else
printf("Sender: Client-sendto() is OK...\n");
printf("Sender: sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));
if (close(sockfd) != 0)
printf("Sender: Client-sockfd closing is failed!\n");
else
printf("Sender: Client-sockfd successfully closed!\n");
return 0;
}//main
/*******************************************EOF***********************/
我已经在我的Debian Linux嵌入式ARM TS-7500单板计算机上运行了这个。
connect()连接套接字之前，请使用bind()设置套接字的本地地址和/或端口。但是，如果客户端和服务器在不同的机器上，则客户端地址永远无法为127.0.0.1。 - Barmar