[英]Count number of clients connected to a server using TCP/IP socket in C programming
[英]Client Port number displaying wrong in server TCP/IP Socket Programming in C
我已經創建了服務器和客戶端以通過套接字進行通信。
但是,當我在localhost下運行時,客戶端端口號顯示為與客戶端綁定到的端口號相同。
但是,如果我在不同的計算機上運行,則客戶端端口號將與客戶端綁定到的端口號不同。
有什么建議嗎?
server.c的代碼
int main(int argc, char *argv[]) {
int socket_file_descriptor, port_number;
struct sockaddr_in server_address;
connection_t *connection;
pthread_t thread;
char *client_address;
int client_port;
struct hostent client;
//check for command line arguments
if (argc != 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
//create socket
socket_file_descriptor = socket(AF_INET, SOCK_STREAM, 0);
if (socket_file_descriptor < 0)
error("ERROR opening socket");
printf("Successfully opened socket\n");
//clear server adress
bzero((char *) &server_address, sizeof(server_address));
//obtain port number
port_number = atoi(argv[1]);
//bind socket to port
server_address.sin_family = AF_INET;
server_address.sin_addr.s_addr = htonl(INADDR_ANY);
server_address.sin_port = htons(port_number);
if (bind(socket_file_descriptor, (struct sockaddr *) &server_address, sizeof(server_address)) < 0)
error("ERROR on binding");
printf("Successfully Binded on port %d\n", ntohs(server_address.sin_port)); //show correct port number
//listen on port
if(listen(socket_file_descriptor,5) < 0)
error("ERROR on listening");
//print message to show connection has been made
printf("Ready and Listening...\n");
//keep server alive with while loop
while(1) {
//accept incoming connections
connection = (connection_t *)malloc(sizeof(connection_t));
connection->addr_len = sizeof(&connection->address);
char ip[connection->addr_len];
connection->sock = accept(*sfd, (struct sockaddr *)&connection->address, &connection->addr_len);
connection->addr = (long)((struct sockaddr_in *)&connection->address)->sin_addr.s_addr;
connection->client_port_number = ntohs(((struct sockaddr_in *)&connection->address)->sin_port);
if(getsockname(connection->sock,&connection->address, &connection->addr_len) == -1) {
printf("Error getting client socket address: %s\n", strerror(errno));
} else {
//client_port_number = ntohs((struct sockaddr_in *)&connection->address).sin_port);
}
if(connection->sock <= 0) {
error("ERROR on accept");
free(connection);
} else {
if(pthread_create(&thread, 0, pthread, (void *)connection) < 0)
error("ERROR creating thread");
printf("Thread Created... Listening on Client:[%s:%d]\n",
inet_ntop(AF_INET,(struct sockaddr *)&connection->addr,ip,connection->addr_len),
connection->client_port_number);
pthread_detach(thread);
}
}
return 0;
}
和client.c的代碼
int main(int argc, char *argv[]) {
int socket_file_descriptor; //socket
int port_number, my_port_number; //server port number , client port number
struct sockaddr_in server_address, my_address; //server IP, client IP
struct hostent * server;
char buffer[256]; //buffer
if(argv < 3) { //command prompt arg [./myC localhost 12345]
fprintf(stderr,"usage %s hostname port\n", argv[0]);
exit(0);
}
port_number = atoi(argv[2]); //server port number = 12345
socket_file_descriptor = socket(AF_INET, SOCK_STREAM, 0); //socket() allows socket_file_descriptor to create socket
if(socket_file_descriptor < 0) {
error("ERROR opening socket");
}
printf("Successfully Opened Socket\n");
server = gethostbyname(argv[1]); //get IP (into network byte) of localhost
if(server == NULL) {
fprintf(stderr,"ERROR, no such host\n");
exit(0);
}
bzero((char *) &server_address, sizeof(server_address)); //memset(server_address)
server_address.sin_family = AF_INET; //AF_INET = symbolic constant
bcopy((char *) server->h_addr, (char *)&server_address.sin_addr.s_addr, server->h_length);
server_address.sin_port = htons(port_number); //htons = 'hostbyte' to 'networkbyte' for type 'short'
printf("Server_Address_Port: %d\n", ntohs(server_address.sin_port)); //ntohs = 'networkbyte' to 'hostbyte' for type 'short'
//Bind client on port
my_address.sin_family = AF_INET;
my_address.sin_port = htons(my_port_number);
if (bind(socket_file_descriptor, (struct sockaddr *) &my_address, sizeof(my_address)) < 0)
error("ERROR on binding");
printf("Client_Address_Port: %d\n", ntohs(my_address.sin_port));
//Connecting to the Server
if(connect(socket_file_descriptor,(struct sockaddr *)&server_address, sizeof(server_address)) < 0) //connect to socket
error("ERROR connecting");
printf("Please enter the message: "); //command prompt requests [send file/ get file / send struct]
bzero(buffer,256);
fgets(buffer,255,stdin);
...
}
並且在server.c的控制台上(在另一台計算機上):
Successfully opened socket
Successfully Binded on port 1234
Ready and Listening...Thread Created... Listening on Client:[172.23.15.197:59540]
並在client.c的控制台上:
Successfully Opened Socket
Server_Address_Port: 1234
Client_Address_Port: 32698
Please enter the message:
當服務器在本地主機上運行時,客戶端端口號與客戶端保持相同的值,即32698(客戶端綁定到的隨機端口)。
代碼本身有什么問題嗎????
提前致謝。
當我在localhost下運行時,客戶端端口號顯示為與客戶端綁定的端口號相同。
正確。 這是同一件事。
但是,如果我在另一台計算機上運行,則客戶端端口號與客戶端綁定的端口號不同。
唯一可能發生的方法是服務器或客戶端位於NAT設備之后。
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