如何在C中为客户端提供特定的IP地址

我试图在C中实现一个简单的客户端和服务器，我在网上找不到如何为客户端设置特定IP地址的示例。 这是我到目前为止所得到的：

sockfd = socket(PF_INET, SOCK_STREAM, 0); if (sockfd == -1) {  } address.sin_family = AF_INET; address.sin_addr.s_addr = inet_addr(); address.sin_port = htons(); 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，我总是得到127.0.0.1

我想改变一些与众不同的东西。

Answer 1

如果您希望客户端使用特定的网络接口进行连接（例如，因为您有多个网卡），那么首先需要在connect之前在该接口的IP地址上调用bind(2) 。 例如，如果您有两个IP地址为192.168.1.100和10.101.151.100的网络接口，那么要使用192.168.1.100地址进行连接，您可以执行以下操作：

 // 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)); 

Answer 2

好的，所以我把解决方案放在一起，同时从计算机上取下ip地址：

  /*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   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  #include  #include  #include  #include  #include  #include  #include  #include  #include  #include  #include  /* 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  \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***********************/ 

我在我的debian linux嵌入式arm ts-7500单板计算机上运行了这个。