socket編程實現一個簡單的多人通信(udp)

在編server程序的時候,在用recvfrom接收信息時出現-1的情況，錯誤爲Invalid argument,在給client_len賦值後問題解決.

client_len = sizeof(struct sockaddr_in);

server程序:

<span style="color:#333333;">/*
  * File Name: socket_udp_server.c
  * Author: eagle
  * mail: [email protected]
  * Created Time: 2015-10-08 18:43
 */

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>

int findclient(struct sockaddr_in client_address, struct sockaddr_in client[], int *client_num);

int main(int argc, char *argv[])
{
	int server_socketfd, client_socketfd;
	int server_len,client_len;
	struct sockaddr_in server_address;
	struct sockaddr_in client_address;
	struct sockaddr_in client[100];//記錄客戶端信息
	int i, byte, client_num = 0;
	char recv[100], send[100];
	
	/*create socket and bind*/
	server_socketfd = socket(AF_INET, SOCK_DGRAM, 0); //創建socket對象
	server_address.sin_family = AF_INET;              
	server_address.sin_addr.s_addr = inet_addr("127.0.0.1"); //主機ip
	server_address.sin_port = 9734;                     //主機端口
	server_len = sizeof(server_address);
	bind(server_socketfd, (struct sockaddr *) & server_address, server_len);

        client_len = sizeof(struct sockaddr_in);
	memset(&client_address, 0, sizeof(struct sockaddr_in));
while(1){
	if((byte = recvfrom(server_socketfd, &recv, sizeof(recv), 0,  //從客戶端接受消息
					(struct sockaddr *)&client_address, //存儲客戶端地址信息
					(socklen_t *)&client_len)) == -1)
	{
	    perror("recvfrom");
		exit(EXIT_FAILURE);
	}

	if(findclient(client_address, client, &client_num) == 0) {
		strcpy(send, "Welcome to chating room");
		if((byte = sendto(server_socketfd, &send, sizeof(send), 0, 
						(struct sockaddr *)&client_address,
						(socklen_t)client_len)) == -1)
		{
			perror("send");
			exit(EXIT_FAILURE);
		}
	} //給剛加入的客戶端發送確認信息

	//printf("recv:%s\n", recv);
	//printf("send:");
	//scanf("%s", send);
	for(i = 0; i < client_num; i++){
		if(client[i].sin_port != client_address.sin_port) {
			client_len = sizeof(client[i]);
			if((byte = sendto(server_socketfd, &recv, sizeof(send), 0, 
							(struct sockaddr *)&client[i],
							(socklen_t)client_len)) == -1)
			{
				perror("send");
				exit(EXIT_FAILURE);
			}
		}
	}
}
//	shutdown(client_socketfd, 2);
//	shutdown(server_socketfd, 2);
	return 0;
}



int findclient(struct sockaddr_in client_address, struct sockaddr_in client[], int *client_num)
{
	int i;
	if(client_num == 0) {
//		client[0].sin_family = client_address.sin_family;
//		client[0].sin_port = client_address.sin_port;
		client[0] = client_address;
		(*client_num)++;
		return 0; //沒有客戶端信息
	}
	else {
		for(i = 0; i < (*client_num); i++) {
			if(client[i].sin_port == client_address.sin_port)
				return 1; //列表中有客戶端的信息
		}
		client[i] = client_address;
		(*client_num)++;
		return 0; //沒有客戶信息
	}
}</span>

client程序:  多人通信的時候需要將client程序複製多份並,改變port值

/*
  * File Name: socket_udp_server.c
  * Author: eagle
  * mail: [email protected]
  * Created Time: 2015-10-08 18:43
 */

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>

int main(int argc, char *argv[])
{
	int socketfd;
	int server_len,client_len;
	struct sockaddr_in server_address;
	struct sockaddr_in client_address;
	int i,byte;
	char recv[100], send[100];
//char recv, send;
	/*hostip 本機ip地址*/
	/*int inet_sock;
	struct ifreq ifr;
	char hostip[15];
	inet_sock = socket(AF_INET, SOCK_DGRAM,0);
	strcpy(ifr.ifr_name, "wlan0");
	if (ioctl(inet_sock, SIOCGIFADDR, &ifr) < 0)
		perror("ioctl");
	strcpy(hostip, inet_ntoa(((struct sockaddr_in *)&(ifr.ifr_addr))->sin_addr));
*/	/*上面部分爲獲取本機ip*/

	socketfd = socket(AF_INET, SOCK_DGRAM, 0); //創建socket對象
	server_address.sin_family = AF_INET;              
	server_address.sin_addr.s_addr = inet_addr("127.0.0.1"); //主機ip
	server_address.sin_port = 9734;                     //主機端口
    server_len = sizeof(server_address);
	
	
	client_address.sin_family = AF_INET;              
	client_address.sin_addr.s_addr = inet_addr("127.0.0.1"); //主機ip
	client_address.sin_port = <span style="color:#ff0000;">9735</span>;                     //主機端口
	client_len = sizeof(client_address);
	bind(socketfd, (struct sockaddr *) & client_address, client_len);

while(1){
	printf("send:");
	scanf("%s", send);
	if((byte = sendto(socketfd, &send, sizeof(send), 0, 
					(struct sockaddr *)&server_address,
					(socklen_t)server_len)) == -1)
	{
		perror("send");
		exit(EXIT_FAILURE);
	}

	if((byte = recvfrom(socketfd, &recv, sizeof(recv), 0,  //從客戶端接受消息
					(struct sockaddr *)&server_address, //存儲客戶端地址信息
					(socklen_t *)&server_len)) == -1)
	{
		perror("recvprom");
		exit(EXIT_FAILURE);
	}
	printf("recv:%s\n", recv);
}
	shutdown(socketfd, 2);
	return 0;
}