你好 TCP 客戶端
此程式是 Hello TCP Server 程式的補充,你可以執行其中任何一個來檢查彼此的有效性。程式流程在 Hello TCP 伺服器上很常見,所以一定要看一下。
這是程式碼 -
#include <cstring>
#include <iostream>
#include <string>
#include <arpa/inet.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
// Now we're taking an ipaddress and a port number as arguments to our program
if (argc != 3) {
std::cerr << "Run program as 'program <ipaddress> <port>'\n";
return -1;
}
auto &ipAddress = argv[1];
auto &portNum = argv[2];
addrinfo hints, *p;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
int gAddRes = getaddrinfo(ipAddress, portNum, &hints, &p);
if (gAddRes != 0) {
std::cerr << gai_strerror(gAddRes) << "\n";
return -2;
}
if (p == NULL) {
std::cerr << "No addresses found\n";
return -3;
}
// socket() call creates a new socket and returns it's descriptor
int sockFD = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
if (sockFD == -1) {
std::cerr << "Error while creating socket\n";
return -4;
}
// Note: there is no bind() call as there was in Hello TCP Server
// why? well you could call it though it's not necessary
// because client doesn't necessarily has to have a fixed port number
// so next call will bind it to a random available port number
// connect() call tries to establish a TCP connection to the specified server
int connectR = connect(sockFD, p->ai_addr, p->ai_addrlen);
if (connectR == -1) {
close(sockFD);
std::cerr << "Error while connecting socket\n";
return -5;
}
std::string reply(15, ' ');
// recv() call tries to get the response from server
// BUT there's a catch here, the response might take multiple calls
// to recv() before it is completely received
// will be demonstrated in another example to keep this minimal
auto bytes_recv = recv(sockFD, &reply.front(), reply.size(), 0);
if (bytes_recv == -1) {
std::cerr << "Error while receiving bytes\n";
return -6;
}
std::cout << "\nClient recieved: " << reply << std::endl;
close(sockFD);
freeaddrinfo(p);
return 0;
}